The lawsuit was filed over an April incident in which a federal marshal erased reporters' recordings of a speech Supreme Court Justice Antonin Scalia gave to high school students.
It was filed in federal court in Jackson. Named as defendants are the Marshals Service, Deputy Marshal Melanie Rube and unidentified John Does.
A.P. assistant general counsel Dave Tomlin said people who enforce the law should know what the law is, especially the basic law that says citizens can't be shaken down by their own government.
Scalia later apologized and also vows he'll make it clear in the future that recording his remarks for the use of the print media won't be a problem.