Breach of Contract?

The SOS of Montana thinks so:

There was no assertion in 1889 that the Second Amendment was susceptible to a collective rights interpretation, and the parties to the contract understood the Second Amendment to be consistent with the declared Montana constitutional right of “any person” to bear arms.

As a bedrock principle of law, a contract must be honored so as to give effect to the intent of the contracting parties. A collective rights decision by the court in Heller would invoke an era of unilaterally revisable contracts by violating the statehood contract between the United States and Montana, and many other states.