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On Thursday, as a new year began and with it a new Congress, Vice President Mike Pence swore in the Senates newly elected and re-elected members on the Senate floor. The event is typically a happy occasion that victorious candidates share with their families, a capstone to what is often a grueling campaign season away from home.

But the celebratory photos that circulate after the fact arent the real deal, and theres a reason for that: Aside from one official photograph each year, photography has been formally banned in the Senate Chamber since the 1950s.

Instead, after Pence officiates the oath of office in the Senate chamber, newly inducted Senators can move to the Old Senate Chamber and do it all over again alongside their families. (Meanwhile, in the much larger House of Representatives, a new Congress is marked by Members taking the oath of office as a group; though that moment has been photographed, the House Speaker may also do individual reenactments as photo-ops for Members.)

Daniel Holt, an assistant Senate historian, tells TIME that the tradition of repeating the oath just for show dates back to as early as the 1930s, when Franklin D. Roosevelts Vice President, John Nance Garner, reenacted oaths in his ceremonial office for the widow of Huey Long, Rose McConnell Long, who briefly became a Louisiana Senator after her husband died, and for New Jersey Sen. William Smathers and Florida Sen. Claude Pepper in the 1930s.

In the 1970s, Vice Presidents began reenacting the oaths with more regularity for the families of newly elected Senators who wanted to be closer to the action, as civilians are generally not permitted on the Senate floor and have to watch from the gallery. After the Old Senate Chamber reopened for tourists in 1976, Vice President Walter Mondale moved the reenactments there in 1981, Holt explains.

From then on it became more of an ingrained tradition, Holt said.

The ceremonial reenactments have become a bigger deal with the advancement of photography. People want keepsakes to remember special occasions by.

This wasnt a huge problem before the 1950s when you didnt have high-speed film and handheld cameras, Holt says.

In fact, Senators have gotten in trouble for using their phones to take photographs and videos on the floor in recent years. On Dec. 20, outgoing Sen. Claire McCaskill was reprimanded for posting a video of the floor while the Senate was not in session. And Im out, the caption read.

United States Senate Majority Leader Mitch McConnells office proceeded to file a complaint with the Senate Sergeant at Arms, which enforces the Senate rules. McCaskill had broken Rule IV, which stipulates that taking of pictures of any kind is prohibited in the Senate Chamber, the Senate Reading Rooms (Marble Room and Lobby), the Senate Cloakrooms, and the Private Dining Room of the Senate.

Reenacting the oaths in the Old Senate Chamber gives Senators a way around Rule IV so they can have precious moments like the one shared by Sen. Chris Murphy and his son Rider in 2013, when the 1-year-old made headlines for raising his hand alongside his father.

Rider Murphy raises his hand just like his father, U.S. Sen. Chris Murphy (D-CT) (L) as he participates in a reenacted swearing-in with his wife Catherine Murphy and U.S. Vice President Joe Biden in the Old Senate Chamber at the U.S. Capitol January 3, 2013

Chip SomodevillaGetty Images

I dont think Vice President [Joe] Biden expected to also swear in my son Rider that day, the Democrat from Connecticut told TIME. Being able to share that moment with my wife and kids meant the world to me and it gave us one of our favorite family photos.

Write to Abby Vesoulis at abby.vesoulis@time.com.

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