Please forgive me if you were not the customer that we discussed this with before (I was not able to see your question history).
If I recall correctly, we discussed this statute in the past and the fact that while MT does have a statute regarding "Declaratory Relief" this statute still requires an actual "Dispute or Controversy" - the courts will not issue what is called an "Advisory Opinion."
In order to have a court opine on the constitutionality of a statute, there must be a dispute over that statute. (Meaning 2 parties with differing interpretations of the statute).
The statute (which, again, if I recall correctly we discussed earlier), is simply a statutory reiteration of the case law rule for declaratory relief. (This is very common as case law is becoming more and more "codified" (where you will see torts, such as fraud, battery, assault, negligence, trespass, etc. - all common law (judge made) torts - placed into statutes).
The statute does not enlarge declaratory relief.
What you are really asking for in having a single party file a case challenging the constitutionality of a statute or rule is for an "Advisory Opinion" as opposed to "declaratory relief" - and the court does not issue advisory opinions.
(Furthermore, and this may further off topic, judicial cannons of interpretation require courts to decide cases by starting with non-constitutional basis or grounds first (so if there is a basis to resolve a dispute on contractual grounds, they will use that, then if there is a basis on statutory, they will use statutory, then constitutional). If there is a conflict between these, the courts will of course address the conflict, but constitutional law interpretation is reserved.)