Near as I can tell that is not actually a real resolution passed by the Montana legislature and therefore it holds no legal standing.

I can find no record of this resolution either in the records of the Montana Legislature or in the archives of the Idaho Observer.

However, it does appear to a patchwork of excerpts of a letter from the Montana Secretary of State to the US Supreme Court. Which would make it similar to letter dozens of states have sent in opposing a collective ruling.

And while the Montana Compact does have the provision described above, it is unclear at this point what legal effect it would have if a collective ruling were passed down.

Montana Warns U.S. Supreme Court

On, Friday, February 22, the State of Montana warned the U.S. Supreme Court that it must uphold the Second amendment as an individual right in Heller or failure to do so would place Montana in violation of its compact with the United States

AN EXTRA-SESSION RESOLUTION OF INDIVIDUAL LEGISLATORS OF THE 60TH MONTANA LEGISLATURE AND OTHER ELECTED MONTANA OFFICIALS URGING THE UNITED STATES SUPREME COURT THAT ANY “COLLECTIVE RIGHTS” HOLDING IN D.C. V. HELLER WILL VIOLATE MONTANA’S COMPACT WITH THE UNITED STATES, THE CONTRACT BY WHICH MONTANA ENTERED THE UNION IN 1889.

The legislature of the state of Montana reasoned in the resolution that, “when the Court determines in Heller whether or not the Second Amendment secures an individual right, the Court will establish precedent that will affect the State of Montana and the political rights of the citizens of Montana; when Montana entered into statehood in 1889, that entrance was accomplished by a contract between Montana and the several states, a contract known as The Compact With The United States (Compact), found today as Article I of the Montana Constitution” and, that it was understood, as Montana entered the Union with the Constitution approved by President Harrison in 1889, the “right” for “any person” to bear arms, “[was] clearly intended as an individual right and an individual right deemed consistent then with the Second Amendment by the parties to the contract…”

Therefore, the 60th Montana Legislature resolved, “1. That any form of ‘collective rights’ holding by the Court in Heller will offend the Compact; and 2. That the Second Amendment and the Montana right to bear arms are both statements securing a preexisting right from government interference, and do not confer any boon of government upon the people; and 3. The level of review for the Montana right to bear arms and for the Second Amendment are specified within those declared rights—‘shall not be infringed’ for the Second Amendment, and ‘shall not be called in question’ for the Montana right to bear arms; 4. Montana reserves all usual rights and remedies under historic contract law if its Compact should be violated by any ‘collective rights’ holding in Heller…”

The resolution by Montana is the strongest warning from a state threatening secession to date. The generally peaceful, “Big Sky” state has a very active gun culture that has influenced the legislature to stand in support of an individual’s right to keep and bear arms.