An amateur film-maker who dressed as the mythical Bigfoot creature is suing the state of New Hampshire after park rangers told him to leave a mountain where he had been engaging with hikers.
Jonathan Doyle’s friends had been filming him on Mount Monadnock.
He argues the state’s requirement that he pay for a permit and get a $2m (£1.2m) insurance bond before he can film violates his free speech rights.
The American Civil Liberties Union (ACLU) is backing Mr Doyle’s lawsuit.
“The underlying activities are humorous, but the principle’s important,” Jon Meyer, a lawyer representing Mr Doyle, told the Associated Press (AP) news agency.
He added: “We don’t believe there’s any legitimate government role in regulation.”
New Hampshire state officials have not commented on the case.
Mr Doyle said no complaints had been made to the state park service in 2009 when he first dressed as Bigfoot, traversed Mount Monadnock, then took off his costume and interviewed bystanders about what they had seen.
“People loved it. It was socially engaging,” the 30-year-old told AP.
But when Mr Doyle announced he would head back to the mountain on 19 September last year, Monadnock park manager Patrick Hummel brought it to the attention of his supervisor in an e-mail entitled “Bigfoot problem on Monadnock… not kidding”.
Mr Hummel then intercepted Mr Doyle during his next outing, barring the film-maker and his friends from filming and requiring them to obtain a permit.
“Jonathan Doyle started this thing with nothing but good humour and intentions,” said Barbara Keshen, a lawyer for the New Hampshire Civil Liberties Union. “But it does have serious overtones.”
Both Ms Keshen and the state of New Hampshire filed motions in court on Tuesday.
Mr Doyle is seeking attorneys’ fees, nominal damages and to be given the opportunity to film on the mountain without obtaining a permit.
Bigfoot, also known as Sasquatch, is a humanoid creature said to wander the wooded wilds of the Pacific Northwest.