CONCORD, N.H. — Bigfoot is taking his First Amendment case to New Hampshire’s top court.

When Jonathan Doyle of Keene donned a Bigfoot costume and set out to videotape staged sightings of the fabled ape-like creature on Mount Monadnock two years ago, state park officials put the kibosh on his escapades, saying Doyle and his friends had failed to pay $100 for a special-use permit 30 days in advance and secure a $2 million bond.

But such requirements stifle free speech and artistic expression and are too broad to pass constitutional scrutiny, say Doyle and the New Hampshire Civil Liberties Union. Defeated at the trial court level, they’ve now climbed to the top of New Hampshire’s legal system, the state Supreme Court.

The state, which won a summary judgment motion in May, argues the permit requirement for organized events is applied fairly and is designed to enhance public enjoyment of the state’s parks “free from unwelcome or unwarranted interference, annoyance or danger.”

Merrimack Superior Court Judge Larry Smukler agreed, saying Doyle’s film “was far more than a simple attempt at spontaneous expression. It was a full-fledged commercial production.”

The justices of the Supreme Court are slated to hear from both sides Thursday.

Doyle first wore his Bigfoot costume on the top of Monadnock on Sept. 6, 2009, then interviewed hikers at random about what they saw. Those interviewed went along with the skit and Doyle posted his video on YouTube.

The 31-year-old Doyle is “a sometimes landscaper, sometimes janitor and a full-time free spirit, filmmaker and performance artist,” NHCLU director Barbara Keshen described in her brief.

He planned to make another movie, “The Capture of Bigfoot,” and The Keene Sentinel newspaper wrote about it. Park manager Patrick Hummel saw the story and emailed a supervisor under the subject line, “Bigfoot problem on Monadnock … not kidding,” according to court documents. In another email, Hummel wrote, “Why does this mountain attract these time wasters?”

On Sept. 19, 2009, Doyle returned to the mountain with five other people in hopes of making the film. Doyle was dressed in casual clothing to film the movie, while a friend wore the Bigfoot costume and two other people wore other costumes. Hummel intercepted the party on the mountain and told them they would need a permit to continue, setting in motion the lawsuit filed in March.

“When you have a regulation that gives unfettered discretion to the people in charge of enforcing it, there’s always the danger they’re going to suppress unpopular activity and unpopular speech,” Keshen said in a recent interview.

Doyle said he thinks officials found his Bigfoot stunt, and the publicity it generated, tacky for a mountain revered by the likes of Henry David Thoreau and Ralph Waldo Emerson.

“If your project’s not to their liking, you’re pushed out or you’re delayed,” Doyle said last week.

“Spontaneity is at the heart of artistic expression and a regulation that completely stifles spontaneous expression is not narrowly tailored,” Keshen wrote in her brief.

But Doyle can’t challenge the fairness of the permit requirement when he made no effort to obtain one or have the permit requirement waived, Assistant Attorney General Matthew Mavrogeorge argued.

Mavrogeorge said two instances of the fee requirement being waived, once for a charity and once for a picnic of National Guard soldiers about to deploy to Afghanistan, were based on good will. Doyle and the NHCLU claim they amounted to “unlawful favoritism.”