Another lawsuit filed over 2025 property tax legislation

Three current and former legislators have filed another lawsuit over Senate Bill 542, a property tax bill signed last year.

State Sen. Greg Hertz, Senate Majority Leader Tom McGillvray and former legislator Keith Regier, all Republicans, jointly filed the lawsuit this week saying SB 542 violates the constitution’s equal protection clause. 

Under SB 542, residential property tax rates differ depending on their market value. The lawsuit, which was filed in Gallatin County, says setting different rates within the same property class violates the constitution.

“Tax relief for one group of Montanans should not come at the expense of unfairly taxing their neighbors. The Montana Constitution protects equal treatment, and we are asking the courts to enforce those protections,” McGillvray said in a press release. “This lawsuit is not about opposing property tax relief. It is about ensuring that tax relief is provided in a manner that respects the constitutional rights of every Montana property owner.”

The lawsuit says equal protection clauses protect individuals from “state action which selects him or her out for discriminatory treatment by subjecting him or her to taxes not imposed on others of the same class.”

Hertz, McGillvray and Regier previously filed a suit over the bill, saying it violated the constitution’s single-subject rule, which says a bill must address just one topic, and it must be clear. That suit, which the state GOP joined on the side of the plaintiffs, is still pending and was also filed in Gallatin County District Court.

“Montanans deserve a property tax system that is fair, transparent, and constitutional,” Hertz said in a press release. “The Legislature has the authority to establish property classifications, but once property is placed within the same class, the constitution requires that taxpayers be treated equally.”

SB 542 was passed during the 2025 session and signed into law by Republican Gov. Greg Gianforte. Some legislators referred to it as a “Frankstein” bill during the sessions, as it drew heavily from other legislation that didn’t pass.

The Governor’s Office did not immediately comment on the suit, but has expressed support for the legislation, saying 80% of Montanans got property tax relief.