With the state attorney general expected to weigh in on a pipeline lawsuit challenging the Massachusetts Constitution’s protection of conservation lands, area officials are calling for a vigorous defense of open space.

Pointing to the lawsuit filed by the Tennessee Gas Pipeline Co. against the state over a proposed natural gas pipeline through state-protected forest in Sandisfield, state Rep. Stephen Kulik said Friday he plans to call for the Massachusetts House to file a “friend of the court” brief in the case.

He said the constitutional provision, called Article 97, will also likely come into play in the controversial Northeast Energy Direct pipeline through Plainfield and eight Franklin County towns.

The pipeline company asserts that approval by the Federal Energy Regulatory Commission  for its Berkshire County route supercedes the state’s constitutional protection of conservation land there.

Kulik called the Tennessee Gas Pipeline plans to override state constitutional protections of open space “probably the greatest overstepping of FERC’s bounds that I can imagine. I would be very pleased if our congressional delegation in its entirety would join with us aggressively weighing in.”

Kulik said Friday, “We have to assert our institutional and constitutional responsibility as a Legislature given to us by the citizens of Massachusetts. It’s a power people have given to the General Court. They certainly didn’t give it to FERC, to some unelected bureaucracy in Washington … I’m hoping for a really aggressive pushback by our attorney general.”

Tennessee Gas Pipeline had hoped the Legislature would grant a waiver from Article 97 to allow the 13.42-mile-long pipeline through Sandisfield, which was approved a week ago by the federal commission. The energy giant sued one day after a Massachusetts legislative committee put that Article 97 waiver request in a procedural graveyard.

Such a waiver requires a two-thirds vote by the Legislature to redesignate protected public land for other use.

The Tennessee Gas Pipeline suit, filed in Berkshire County Superior Court, seeks eminent domain of 21.5 acres in Sandisfield, with easements in the affected part of Otis State Forest. The suit came even as Sandisfield residents formally appealed the federal commission’s approval for the project — pointing out that the state’s constitutional issue and federal water-quality permits had not yet been settled.

Kulik addressed a group Thursday night participating in a Sugar Shack Alliance protest walk against the pipeline, advising the group, trained in direct action, to focus on the Sandisfield issue now, although he stopped short of calling for civil disobedience.

Although Kulik said it’s probably good to have the question raised and resolved over the Sandisfield case rather than waiting for it to surface for the Northeast Energy Direct project, the federal commission is now reviewing the pipeline route through Plainfield, Ashfield, Conway, Shelburne, Montague, Deerfield, Erving, Montague, Northfield and Warwick.

Kulik said conservation land was established with money “raised by the people of Massachusetts. Everyone in the state who cares about natural resources protection needs to be concerned about this, especially because there is zero benefit from any energy or public policy perspective to the people of Massachusetts. That’s like really rubbing our noses in this.”

Senate President Stanley Rosenberg, D-Amherst, on Thursday called the lawsuit “the beginning of resolving the question” over federal preemption and the state constitutional provision. He, like other legislators, said he would expect the attorney general’s office to respond for the state and predicted the case “could go all the way to the U.S. Supreme Court.”

Asked about the attorney general’s plan in the case, a spokesman said the attorney general will defend the state and the Department of Conservation and Recreation in this matter and plans to file an opposition prior to the hearing.

Kathryn Eiseman of Pipeline Awareness Network of Massachusetts said, “This is where the rubber hits the road with respect to Article 97 … Many people are just waking up to the importance of this land in Otis State Forest. Not only are some of the last remaining old-growth hemlock stands in Berkshire County directly threatened, the whole framework under which land is protected in our commonwealth, under our Constitution, is potentially threatened.”

Rather than trying to circumvent the protected Spectacle Pond property donated by the Massachusetts Audubon Society, she said, Tennessee Gas Pipeline appeared to have “purposely targeted it and are digging in their heels, with the hope to establish authority to run roughshod through our protected lands across the commonwealth.”

Although it’s unclear exactly whether  federal preemption conflicts with Massachusetts’ unique constitutional provision giving the Legislature sole authority over conservation land, Boston attorney Richard Kanoff, who represents Pipeline Awareness Network of the Northeast as well as Montague, Gill and Northfield in cases involving the Northeast Energy Direct project, said “This is a really significant issue, and there are a lot of important questions involved. I would be surprised if the attorney general doesn’t file. It raises significant concern about whether Article 97 means anything, or whether a 401 water quality certificate means anything.”

A hearing on Tennessee Gas Pipeline’s case seeking to exercise eminent domain over the land in question is scheduled for March 30. There is a March 31 cutoff under the federal Endangered Species Act to protect migratory birds that use the trees for spring nesting, although the company has asked the U.S. Fish and Wildlife Service for that deadline to be extended until May 1. In its court filing, it seeks authority for condemnation by April 15.