A video appearing to show agents of the U.S. Border Patrol boarding an interstate bus in Fort Lauderdale, Florida went viral on Twitter over the weekend. The agents move down the bus' aisle, asking each passenger to provide some form of documentation proving that they are in the country legally.

Watch below:

.@CustomsBorder got on a Greyhound bus yesterday at 4:30pm in Fort Lauderdale and asked every passenger for their papers and to prove citizenship. Proof of citizenship is NOT required to ride a bus! For more information about your rights, call our hotline: 1-888-600-5762 pic.twitter.com/rWJn61o8VP — FLImmigrantCoalition (@FLImmigrant) January 20, 2018

Not surprisingly, the video has drawn largely critical reactions. Officers demanding that passengers "show their papers" during a suspicionless sweep of a bus not crossing any international boundary? It may seem more like a relic from history or a scene from dystopian fiction than something most Americans expect to encounter in their daily travels.

But not if you've been paying attention. Sadly, such suspicionless immigration sweeps are more common than many people think. Far from being a rare action by rogue agents, these "roving patrols" are a routine part of Border Patrol operations, and their frequency has been slowly increasing since 9/11.

Blame the Supreme Court for the practice's persistence. In a series of decisions going back to the 1970s, the Court has conferred immigration and customs authorities with ever-increasing power to detain, question, and search people "within a reasonable distance from any external boundary of the United States." The feds have interpreted this to mean that immigration agents may conduct enforcement operations at any location within 100 miles of a land or sea border. That area encompasses most of America's major cities, and it is home to roughly two thirds of the country's residents.

Immigration authorities' power within this zone, the Supreme Court said, includes the power to detain travelers long enough to elicit "response to a brief question or two and possibly the production of a document evidencing a right to be in the United States," even without any articulable suspicion.