HELENA — Gov. Steve Bullock on Friday signed a bill containing the last and most contentious of seven tribal water compacts in Montana.

The Democratic governor signed Senate Bill 262 surrounded by about 150 supporters, including bill sponsor Sen. Chas Vincent and Confederated Salish and Kootenai Tribal Chairman Vernon Finley.

The historic measure, decades in the making, details a water use agreement among the Confederated Salish and Kootenai Tribes and the state and federal governments.

Congress will take up the compact next. State attorneys say it could be years before the agreement is approved by Congress and moves to the tribes for implementation

Vincent helped re-negotiate the deal after he and other lawmakers in the 2013 session shot down a compact that was seen as less friendly to non-tribal irrigators.

The agreement now includes a delivery entitlement that ensures non-tribal farmers and ranchers continue to receive the amount of water they have historically used, and a provision requiring the tribes to share water during droughts.

Vincent, a Libby Republican, said compromises made by the Confederated Salish and Kootenai Tribal Council made it possible for him and other lawmakers to support and pass the compact.

“Without their willingness to sit down and listen to our concerns and agree to our changes, we would not be here today,” Vincent said, thanking Finley and the tribes.

He and Rep. Steve Fitzpatrick, R-Great Falls, who carried the bill in the House, said the tribes made concessions that might not have been necessary if they had instead asked a court to recognize their time immemorial right to use water.

“That’s basically the whole agreement — let’s share the resources and let’s be good neighbors and let’s work together for a common goal,” Finley said.

Of the 34 U.S. states with tribal reservations, Vincent said Montana is the only one that has negotiated water rights outside of court.

“We’re kind of the golden child of western water law in a lot of ways,” Vincent said after SB262 passed the House on April 16. “In dealing with these federal reserve rights, we have chosen to negotiate and settle rather than argue for 10 years in court.”

A lawsuit filed Monday seeking to restrain the governor from signing the bill was pending at the time of the ceremony on Friday. The eight irrigators who filed the claim spoke against the compact throughout the legislative vetting process, saying they would lose water if the tribes are granted oversight of the commodity.

“There is no underlying trick that we’re trying to pull,” Finley said. “My hope is that history will let them finally understand that that’s the case and they won’t keep wasting their money on frivolous lawsuits.”