A coalition of groups says private landowners are illegally blocking public trails in the southern Crazy Mountains in Custer Gallatin National Forest between Big Timber in Livingston and that the Forest Service isn't doing anything about it.

The Western Environmental Law Center sent a letter to the Forest Service Wednesday on behalf of the Montana chapter of Backcountry Hunters and Anglers, Friends of the Crazy Mountains, Enhancing Montana's Wildlife and Habitat, Skyline sportsmen Association and five individuals.

It requests a meeting with forest officials to discuss the coalition's concerns.

The letter also serves as notice that it intends to sue the agency for failure to protect and defend public access rights in the Crazy Mountains if it doesn't "provide a meaningful response and/or propose a timely solution."

In the letter, members of the coalition say owners of land within the forest boundary are locking gates and posting "no trespassing," "permission required" and "keep out signs" on public trails.

Sometimes, they add, they are intimidating members of the public.

Those actions prompted the coalition to consider legal action.

John Sullivan, chairman of the Montana chapter of Backcountry Hunters and Anglers, said in an interview that the issue is not whether the trails are public.

"Our contention is that the Forest Service is not doing its job to keep these trails open," Sullivan said.

Marna Daley, public affairs officer for the Custer Gallatin National Forest, said the agency will digest the notice of intent to sue and then determine how best to proceed.

In one step to resolve access disputes, the Forest Service had been hoping to reroute the Porcupine Lowline trail this summer, she said.

It isn't clear how the letter from the coalition will affect that work.

"Access disputes in the Crazy Mountains have been going on for a long time and receiving the notice of intent was really disheartening for us because we feel over the last couple of years more progress to secure long-term access to the Crazy Mountains has been made than in decades," Daley said.

In the letter, the coalition says that the Forest Service, in it's work on the rerouting of the Porcupine Lowline trail to resolve the access issues, never insisted that the landowner first end the practice of blocking public access.

Also in dispute are Elk Creek, Sweetgrass, East Trunk and Swamp Lake trails.

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Backcountry Hunters and Anglers' Sullivan says it got involved in the situation two years ago after being contacted by Rob Gregoire who was cited by a sheriff's deputy for trespassing on Forest Trail 136 while elk hunting. A district ranger for the forest had told him that the Forest Service considered the trail public.

"We hope we can work with them and not go to court," Sullivan said.

Sometimes, he added, going to court is what it takes to resolve an issue.

The southern half of the Crazy Mountains are managed by the Custer Gallatin National Forest. The northern half is in the Helena-Lewis and Clark National Forest.

It's a "beautiful landscape," the Forest Service's Daley said, but access disputes have simmered for decades.

"There is a lot of checkerboard ownership in the Crazy Mountains," Daley said. "A lot of ranchers and private individuals have ownership in that landscape. So access has been difficult for sure because in most cases public trails have to cross private land to gain access to public land."

In the letter, the coalition says the obstruction by landowners has had a "chilling" effect on the public access in the area.

The coalition says it has reviewed Forest Service documents that were obtained through Freedom of Information requests.

There is no question, the groups argue, that the public has had the right of public access to the five illegally blocked trails for almost a century.

That's acknowledged in a number of internal emails and memorandum that the groups reviewed, the letter says.

The letter cites an instance in 2009 when then-District Ranger Ron Archuleta drafted a letter to the private landowners requesting that "keep out" and "trail closed" signs posted on Porcupine Lowline Trail and a locked gate near Porcupine Lowline Cabin be removed.

The groups say that nothing came of that letter and the signs and gate remain up.

"Similar and more recent efforts by the current district ranger to respectfully (but forcibly) address the continued and on-going illegal obstruction of these five public trails has also been rebuffed," the coalition says in the letter to the Forest Service. "This district ranger was also recently removed and reassigned after correctly informing the public that it need not (and should not) ask for permission from private landowners to use existing public trails on service maps, including the trails at issue here. He was later restored to his district ranger post because he was correct: the public does not need permission to access public trails."

Daley, of Custer Gallatin National Forest, said Forest Service priorities are improving access first on the west side of the Crazy Mountains, then a potential land exchange in the southern end and finally securing long-term access on the east side.

The agency has been part of a working group to look at access options, she said.