Still, the government maintained that what the agents did was lawful, and Cline’s explanation for that belief is the heart of the problem. It all comes back to that crucial word, “arrest.” DHS says pulling a man off the street and carrying him away in an unmarked van was just a “simple engagement.” “It was not a custodial arrest,” Cline said. In other words, the officers supposedly complied with the Fourth Amendment because, in Cline’s view, they didn’t need probable cause: There was no arrest, he says.

This assertion is glaringly wrong — and it has been for 40 years, since the Supreme Court’s 1979 opinion in Dunaway v. New York. In that case, the justices had to decide whether police officers violated the Fourth Amendment when, without probable cause, they took someone “into custody, transported him to the police station, and detained him there for interrogation.” Their answer, reaffirmed over the years, was unequivocal: Such conduct is “indistinguishable from a traditional arrest,” which need not be accompanied by bureaucratic processes like fingerprinting, booking or a formal arrest record to count as an arrest for purposes of the Fourth Amendment.

So, according to the Supreme Court, the federal agents in that video really did arrest the man they put in the van — without probable cause, by the government’s own admission. That means they violated the Fourth Amendment.