I'd submit both arguments -
While at the gun show, another angle came to me: the "loaded" argument may be another good one to try alongside the constitutional one.
Here's the deal: if a law is so vague, or contains terms that are undefined ("unloaded"), then the average citizen cannot reasonably expected to determine what the prohibited conduct is. Therefore, how can the courts say what is prohibited when there are vague or undefined terms? Accordingly, the citizen has been denied due process because he was not given full and fair warning of what conduct is prohibited, and the case has to be dismissed for lack of due process.
Stay with me here -
Other states define "loaded." Doesn't Utah have some hyper-technical definition of "loaded" - something like "two mechanical actions/steps away from firing?" Contrast that with Idaho (no definition), and other surrounding states - OR, WA, MT, WY, NV - do they define it? The lack of specific definition, arguably, leads to a vagueness that the average citizen cannot know whether his gun is technically "loaded" or "unloaded" given the lack of clarity in the law, as opposed to other states that specify when a gun is "loaded."
It's not a terribly strong argument, but when it's one's liberty, freedom and finances are at stake, they should make every argument possible in an effort to persuade the judge.
There's no prohibition against making alternative arguments to the court; I'd argue both the constitutional one and the due process/vagueness to the judge.