The police have limited powers to uphold the law, including things like arresting murderers. They don't have the power to arbitrarily order people to do whatever they want. If an officer asks you to do something when you're not committing a crime or endangering anyone you are allowed to say no.
For all Americans talk about having rights and freedom you do seem incredibly quick to give them up in the face of authority.
For all Americans talk about having rights and freedom you do seem incredibly quick to give them up in the face of authority.