“It’s terrifying to be assaulted by people that you can’t be sure are law enforcement and who seem to be hiding their identity from you,” David Sklansky told me. He’s a law professor at Stanford and an expert on policing. He said there are times when secrecy by authorities can be justified, but it should be the exception, not the rule.

“The seizure of people by agents of the state who don’t identify themselves as agents of the state is a tool that has a long and ugly history of being used by authoritarian regimes,” he said.

Sklansky points out that accountability doesn’t necessarily require a name or face. Although there is no law that requires it, federal authorities could simply put their badge number and agency name someplace visible. Voila! Accountability and safety for officers.

“Lots of law enforcement works this way,” he said.

Failing to provide any kind of trustworthy identification causes its own dangers, both Sklansky and Goldstein told me. People are required by law not to interfere with law enforcement doing their duty. But if you don’t know it’s law enforcement and fear you are witnessing an attack or are the victim of one, the situation is different.