Opinion analysis: Reasonable mistakes of law by police do not violate the Fourth Amendment
The exercise of police discretion to stop people on the street is front and center in todays headlines. In this case, a North Carolina policeman stopped Heiens car because it had a brake light that did not work. During the stop, Heien consented to a search of the car, which yielded cocaine in a duffle bag and Heiens ultimate conviction for attempted drug trafficking. On appeal, the North Carolina appellate courts surprisingly ruled that the outdated state vehicle code required only one working brake light (a stop lamp, in the words of the statute); therefore, there had been no violation of law that would permit the stop. The officer made no error about the facts; but he had been mistaken about the meaning of the law. However, the North Carolina Supreme Court ruled, the officers mistake about this law was reasonable, and for that reason the Fourth Amendment right to be secure from unreasonable seizures was not violated. This mornings opinion in Heien v. North Carolina affirms that holding.
Chief Justice Roberts announcing the opinion. (Art Lien)
The constitutional law of reasonableness The vague word unreasonable in the Fourth Amendment is a lawyers playground, and questions about what sort of circumstances constitutionally permit law enforcement seizures have thus plagued the federal courts since the Fourth Amendment was adopted. In 1813, Chief Justice John Marshall wrote that the constitutional standard is circumstances which warrant suspicion a relatively unspecific and therefore unhelpful standard. But its unhelpfulness flows from the generality of the amendment itself. It is not judge-made policy; it is constitutional text.
Over the years the Court has honed its thinking about what constitutes probable cause to stop or search (for example, Illinois v. Gates in 1983), and in Terry v. Ohio in 1968 the Court famously ruled that even brief stops on the street require at least specific and articulable reasonable suspicion, not just hunches. The Court has subsequently made clear that even when police are mistaken about facts, their stops do not violate the Constitution if their mistakes are reasonable.
Todays opinion
Today, in an opinion by Chief Justice John Roberts, a majority of eight Justices affirmed that there is no reason why this same result should not apply when reached by way of a similarly reasonable mistake of law. The Court conceded and Justice Sonia Sotomayor, the lone dissenter, agreed that no precedent of the Court has expressly answered this reasonable mistake of law question (scarcely a peep). The Court noted, however, that as early as 1809, the Supreme Court ruled that a reasonable mistake of law about probable cause permitted a customs seizure under a federal statute. By 1860, this general principle had been adopted in numerous [lower court] cases. While acknowledging that the statutory customs cases were not directly on point for the constitutional question, the Court also explained that no decision of this Court in the two centuries since has undermined that understanding that reasonable mistakes of law can excuse governmental action. In fact, the Court explained that in more recent cases, such as Michigan v. DeFillippo, it had found no Fourth Amendment violation even when governmental searches were based on state statutes later declared unconstitutional. (Justice Sotomayor strongly disagreed with this reading.)
Arguing for Heien, attorney Jeffrey Fisher had struggle[d] to limit the Courts ruling solely [to] the exclusionary rule that is, the remedy in lieu of a more general ruling about the right (that is, whether the officers stop was an unreasonable violation of the amendment). This was likely an attempt to preserve some relief for Heien on remand, because North Carolina purportedly has not adopted a good faith exception to the exclusionary rule. But there will be no remand for further proceedings under todays ruling, which flatly affirmed the state courts ruling. The Court said that DeFillippo was plainly a decision about the meaning of probable cause, and thus its holding regarding a reasonable mistake of law cannot be transform[ed] into an exclusionary rule decision. So in this case, because the officers mistake about the meaning of North Carolinas vehicle code was reasonable, there was no violation of the Fourth Amendment in the first place.
(By contrast, the Court also noted that an individual officers mistaken view, no matter how reasonable, that he has complied with the Fourth Amendment, does not undermine a reviewing courts ultimate conclusion that governmental actions have violated the Fourth Amendment even though it might affect the remedy. This significant reservation regarding the scope of the Courts ruling is emphasized in footnote 1 of Justice Elena Kagans concurring opinion, and should not be overlooked.)
The majoritys limitations, and two separate opinions
Importantly, particularly in light of recent controversies, the Court observed that the standard of reasonableness for mistakes of law is not as forgiving as some might have it. An officers legal error must be objectively reasonable, and not based on a particular officers subjective understanding or on a sloppy study of the laws he is duty-bound to enforce. Thus, the Court suggested, an officer must learn[] the law, and I would expect that the familiar standard of a reasonably well-trained officer will be rigorously applied by lower courts when confronted with Heien errors in the future.
Read the original:
Opinion analysis: Reasonable mistakes of law by police do not violate the Fourth Amendment
- Politically Unstable: Flock cameras flip the Fourth Amendment on its head - Washington Times - August 18th, 2026 [August 18th, 2026]
- Administrative inspections are not a shortcut around the Fourth Amendment - Police1 - August 11th, 2026 [August 11th, 2026]
- Pete Buttigieg, the Supreme Court, and the Fourth Amendment - SCOTUSblog - August 11th, 2026 [August 11th, 2026]
- Do Flock cameras violate the Fourth Amendment? Here's what federal courts have ruled - NBC Connecticut - August 11th, 2026 [August 11th, 2026]
- Flock Cameras Violate Highway Safety Standards As Well As The Fourth Amendment - Jalopnik - August 9th, 2026 [August 9th, 2026]
- Mistaken identity and the Fourth Amendment - Police1 - July 24th, 2026 [July 24th, 2026]
- The Fourth Amendment Moves to the Cloud: Chatrie v. United States and the Future of Digital Privacy - JD Supra - July 6th, 2026 [July 6th, 2026]
- Your Phone Location Data Is Now Protected By The Fourth Amendment. Here's Why That Matters - IFLScience - July 6th, 2026 [July 6th, 2026]
- Elena Kagan Just Bolstered the Fourth Amendment in a Badly Needed Way - Slate Magazine - July 1st, 2026 [July 1st, 2026]
- CAC Release: In Important Victory for Digital Privacy, Supreme Court Holds that Even Short-Term Police Monitoring of Cell-Phone Location Information... - July 1st, 2026 [July 1st, 2026]
- Justices rule that cellphone location histories are protected by the Fourth Amendment - The Record from Recorded Future News - July 1st, 2026 [July 1st, 2026]
- Unpacking Chatrie v. US: Data, Privacy, AI, and the Fourth Amendment - R Street Institute - July 1st, 2026 [July 1st, 2026]
- In big win for Fourth Amendment advocates, the Supreme Court says 'geofence warrants' count as a 'search' - Reason Magazine - July 1st, 2026 [July 1st, 2026]
- User location data that Google & Apple have is protected by Fourth Amendment, says SCOTUS - AppleInsider - July 1st, 2026 [July 1st, 2026]
- Elena Kagan Just Bolstered the Fourth Amendment in a Badly Needed Way - Yahoo - July 1st, 2026 [July 1st, 2026]
- Your location data is now officially protected by the fourth amendment here's what that means for you - Tom's Guide - July 1st, 2026 [July 1st, 2026]
- Nag: Digital privacy and the Fourth Amendment - Daily Emerald - June 12th, 2026 [June 12th, 2026]
- Artificial Intelligence and the Fourth Amendment: Two Emerging Legal Issues - Every CRS Report - May 9th, 2026 [May 9th, 2026]
- Justices appear mixed on whether geofence warrant violated the Fourth Amendment - SCOTUSblog - May 1st, 2026 [May 1st, 2026]
- House Votes to Continue Subverting the Fourth Amendment - Cato Institute - May 1st, 2026 [May 1st, 2026]
- SCOTUS Hears the Next Big Fourth Amendment Fight Over Digital Location Data - The National Law Review - May 1st, 2026 [May 1st, 2026]
- The Fourth Amendment, Explained and Accountable - American Enterprise Institute - AEI - May 1st, 2026 [May 1st, 2026]
- A Fork in the Road for the Fourth Amendment - Law.com - May 1st, 2026 [May 1st, 2026]
- Editorial: A bipartisan defense of the Fourth Amendment - Orange County Register - March 26th, 2026 [March 26th, 2026]
- A bipartisan defense of the Fourth Amendment - Olean Times Herald - March 26th, 2026 [March 26th, 2026]
- Civil Society Coalition Condemns EARN IT Act for Failing to Protect Children While Threatening Encryption and First and Fourth Amendment - New America - March 15th, 2026 [March 15th, 2026]
- Pegasus spyware and Section 702 surveillance place the Fourth Amendment under siege - Washington Times - March 15th, 2026 [March 15th, 2026]
- Students head to Ohio Mock Trial state finals to argue Fourth Amendment rights - News and Sentinel - March 9th, 2026 [March 9th, 2026]
- Cell Tower Dump and Geofence Warrants: The NJ Supreme Courts Next Fourth Amendment and Privacy Issue? - Law.com - March 7th, 2026 [March 7th, 2026]
- NCLA Asks Supreme Court to Rule that Geofencing Warrants Violate the Fourth Amendment - myvillager.com - March 7th, 2026 [March 7th, 2026]
- Former ICE instructor will testify as whistleblower that agents taught to violate Fourth Amendment - The Daily Gazette - February 24th, 2026 [February 24th, 2026]
- ICE Administrative Warrants and the Fourth Amendment: A Response to the DHS General Counsel - Just Security - February 22nd, 2026 [February 22nd, 2026]
- Administrative Warrants, Immigration Arrests, and the Fourth Amendment - Cato Institute - February 22nd, 2026 [February 22nd, 2026]
- Federal judge in WV rules that masked ICE agents violate the Fourth Amendment - The Real WV - February 22nd, 2026 [February 22nd, 2026]
- Op-Ed | The Trump administration has turned the Fourth Amendment on its head - amNewYork - February 22nd, 2026 [February 22nd, 2026]
- Do Construction Workers Have Fourth Amendment Rights? A Federal Court Will Decide. - Reason Magazine - February 14th, 2026 [February 14th, 2026]
- DHS makes a mockery of the Fourth Amendment | Guest Column - Iowa City Press-Citizen - February 14th, 2026 [February 14th, 2026]
- Democrats want ICE to comply with the Fourth Amendment. Right-wing media are trying to muddy the waters. - Media Matters for America - February 9th, 2026 [February 9th, 2026]
- Fourth Amendment questions we should all be asking - WyomingNews.com - February 9th, 2026 [February 9th, 2026]
- Feds Are Stealthily Violating Millions of Americans Fourth Amendment Rights - New Civil Liberties Alliance - February 9th, 2026 [February 9th, 2026]
- Half the Answer #63: SCOTUS, the Fourth Amendment, and the Resistance - liberalcurrents.com - February 9th, 2026 [February 9th, 2026]
- Have we kissed the Fourth Amendment goodbye? - The Hill - January 30th, 2026 [January 30th, 2026]
- Maryland man argues arrest using cellphone tracking device violates the Fourth Amendment - Courthouse News - January 30th, 2026 [January 30th, 2026]
- Supreme Court agrees to hear a Fourth Amendment case regarding geofence warrants - Brookings - January 30th, 2026 [January 30th, 2026]
- ICEs Actions Are Gutting the Fourth Amendment - Bloomberg.com - January 30th, 2026 [January 30th, 2026]
- ICE and CBP are slicing the Fourth Amendment - Washington Examiner - January 30th, 2026 [January 30th, 2026]
- Sean Hannity argues with radio caller concerned ICE may be delving into some things that could be against the Fourth Amendment - Media Matters for... - January 18th, 2026 [January 18th, 2026]
- Howey: Putting on a show, at the expense of the Fourth Amendment - The Herald-Times - January 16th, 2026 [January 16th, 2026]
- Case v. Montana and the General Law Approach to the Fourth Amendment - Divided Argument | Substack - January 16th, 2026 [January 16th, 2026]
- Op-Ed | Abducting a despot: When U.S. justice leaves the Fourth Amendment behind amNewYork - amNewYork - January 11th, 2026 [January 11th, 2026]
- Fourth Amendment Tested As ICE Plans Door-To-Door Enforcement - International Business Times UK - January 11th, 2026 [January 11th, 2026]
- Opinion | Flock data collection violates the Fourth Amendment - The Durango Herald - December 31st, 2025 [December 31st, 2025]
- The Fourth Amendment's Erratic Year at the Supreme Court - Reason Magazine - December 27th, 2025 [December 27th, 2025]
- JoCo supervisors hear from public about Fourth Amendment protections - The Daily Iowan - December 14th, 2025 [December 14th, 2025]
- Fourth Amendment rights should not depend on your proximity to the border - Pacific Legal Foundation - December 14th, 2025 [December 14th, 2025]
- Duke students and faculty push the university to become a fourth amendment campus as ICE presence grows - Times of India - December 10th, 2025 [December 10th, 2025]
- FPUA OKs fourth amendment for island-to-mainland wastewater shift - Hometown News Treasure Coast - November 30th, 2025 [November 30th, 2025]
- Biometric Surveillance and the Fourth Amendment - Law.com - November 28th, 2025 [November 28th, 2025]
- Collateral Damage, Episode Five: What Fourth Amendment? - The Intercept - November 7th, 2025 [November 7th, 2025]
- Does the Fourth Amendment Really Protect People of Color? - EBONY Magazine - November 7th, 2025 [November 7th, 2025]
- Too poor for privacy? People v. Maki and the tent as a Fourth Amendment frontier - Daily Journal - October 28th, 2025 [October 28th, 2025]
- Traffic Stops, Terry Stops, Policing, the Fourth Amendment, and Your Rights - Legal Talk Network - October 24th, 2025 [October 24th, 2025]
- There goes the fourth amendment - The Tartan - October 24th, 2025 [October 24th, 2025]
- Hoover Webinar with Orin Kerr on His "The Digital Fourth Amendment" - Reason Magazine - October 21st, 2025 [October 21st, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - Live 5 News - October 19th, 2025 [October 19th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WLBT - October 19th, 2025 [October 19th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WIS News 10 - October 19th, 2025 [October 19th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WDTV 5 - October 19th, 2025 [October 19th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - localnewslive.com - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WCTV - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - fox10tv.com - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WABI - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - fox8live.com - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WSAZ - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WAVE News - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - WAFB - October 17th, 2025 [October 17th, 2025]
- Supreme Court to hear arguments in case tied to Fourth Amendment - KY3 - October 17th, 2025 [October 17th, 2025]
- Opinion | To the Fourth Amendment: You Were Great While We Knew You - Common Dreams - October 13th, 2025 [October 13th, 2025]
- Treasury Department surveillance at the southern border faces Fourth Amendment challenges - Reason Magazine - October 9th, 2025 [October 9th, 2025]
- Commentary: The Fourth Amendment will no longer protect you - The Daily Gazette - October 4th, 2025 [October 4th, 2025]