Montana GOP Joins Lawsuit to Invalidate Gianforte-Backed Property Tax Law

HELENA, Mont. — The Montana Republican Party formally joined a lawsuit seeking to nullify a major property tax law signed by Republican Gov. Greg Gianforte, escalating an internal party conflict over the state's tax policy. In a brief filed on April 16 in Gallatin County District Court, the Montana Republican State Central Committee sided with two current and one former Republican legislator who allege the 2025 law, known as Senate Bill 542, is unconstitutional. The lawsuit, originally filed in January 2026, was a response to steep property tax increases that followed Montana's recent real estate boom. SB 542 was passed by the 2025 Legislature and championed by Gov. Gianforte as a measure that provided relief to 80% of Montana homeowners through new tax rates and $95 million in rebates. The legal challenge, now bolstered by the state party apparatus, argues the law was the product of an unconstitutional legislative process. For business owners, this level of political infighting over core tax legislation creates significant uncertainty. When a state's ruling party sues to overturn a law signed by a governor from that same party, it signals deep instability in fiscal policy that can disrupt long-term financial planning. While this lawsuit centers on residential property, any court decision that invalidates a major tax bill on procedural grounds could set a precedent that impacts future business tax legislation. Our experience shows that businesses thrive on predictability. Sudden legal challenges can complicate everything from budgeting and forecasting to investment decisions. Navigating this landscape requires diligent monitoring and expert guidance. This is a core part of our tax preparation and compliance services at C&S Finance Group LLC, where we help businesses understand and adapt to rapidly changing state tax environments. For assistance with these complex matters, business owners can contact C&S Finance Group LLC at csfinancegroup.com. The plaintiffs in the case are Republican State Sens. Greg Hertz of Polson and Tom McGillvray of Billings, along with former Kalispell legislator Keith Regier. Their core argument is not necessarily with the substance of the tax changes but with the process by which SB 542 became law. The lawsuit alleges the bill was a cobbled-together package that violated the Montana Constitution's single-subject rule, which requires a bill's title to accurately reflect its contents. The plaintiffs contend the bill was the product of "secret deals" that cut out public input. According to the court filings, the original version of SB 542 was gutted and replaced with controversial provisions from other bills, a legislative maneuver often called "log rolling." The suit specifically names Rep. Llew Jones, a Conrad Republican, as having orchestrated the effort, allegedly misleading citizens who testified in support of what they believed was a simple property valuation freeze. The lawsuit quotes Jones as admitting that including cash rebates was necessary to pass the broader bill, stating, "sometimes, that's the cost of doing business up here." This legal battle is a public manifestation of a deep and ongoing rift within the Montana Republican Party. The conflict pits a more hardline conservative faction, which includes the plaintiffs and the state party leadership, against a group of more moderate Republicans aligned with Gov. Gianforte and Rep. Jones. This division was starkly evident during the 2025 legislative session when nine Republican senators, dubbed "The Nine," frequently sided with Democrats to form a "working majority," passing major bills like the state budget over the objections of their party's leadership. The state GOP later censured those senators, and this lawsuit represents a continuation of that power struggle. Gov. Gianforte, who is not a named defendant in the case, has consistently defended SB 542. He has warned that a successful lawsuit could invalidate the tax rates and rebates that have already been distributed to Montana homeowners. In March, the governor unsuccessfully petitioned the Montana Supreme Court to take over the case from the district court and issue an expedited ruling on its constitutionality, but that request was denied. The lawsuit names the State of Montana, the Department of Revenue, and its director, Brendan Beatty, as defendants. The plaintiffs argue that the law unfairly raises taxes on certain properties, such as multigenerational family cabins. The three legislators who initiated the suit also stated in their original filing that their own property tax bills increased under the new legislation. Sen. Hertz has publicly pushed back against the governor's concerns, suggesting that the court would not force residents to return property tax rebates they have already received. The case will now proceed in Gallatin County District Court. Its resolution will not only determine the fate of a key piece of Montana's property tax code but will also serve as a significant marker in the ongoing battle for control and direction within the state's dominant political party.