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Then your only action would be against the county employee - for acting outside the scope of their authority. Yes, you have a cause of action against them - but not if you don't have damages.
I realize the prohibition of not being able to go where you want to go are damages. I believe that the wrongful and unauthorized restriction of your not being able to use public property would be a violation of your "life, liberty, and the pursuit of happiness".
"Life, liberty, and the pursuit of happiness" is one of the most famous phrases in the United States Declaration of Independence. These three aspects are listed among the "inalienable rights" of man.
However, in searching the law - I don't see that you have a cause of action unless they would have arrested you.