Answer:
With no pending prosecution, a federal plaintiff may seek a declaratory judgement that a state statute would be unconstitutionally applied against him in a threatened future prosecution.
Explanation:
The action of the police in this context can be considered as the violation of the first amendment under the protection of free speech, Similar case occurred in 1974 (Steffel v. Thompson, 415 U.S. 452). In that similar case, the companion who arrested was given a freedom since the arrest is considered as unconstitutional.