Washington, D.C. — The nation's capital challenged President Donald Trump's takeover of its police department in court on Friday, hours after his administration stepped up its crackdown on policing by naming a federal official as the new emergency head of the department, with all the powers of a police chief.

With federal and local officers on D.C.’s streets, here’s what to know about what law enforcement agencies can legally order you to do — and what they can’t.