I ran into a similar weapons problem a few years back. (but not with 500 weapons!) When the DA filed charges, I didn't hire Johnny Cochran, I hired a local attorney, a real sweet gal (outside the courtroom), but in the court room she had more in common with a rabid wolf, than a human being. When you see the prosecutor physically wince in pain at her quick thinking, her logic and acid tongue, you know you've hired the right person. Hell, even if you don't win, you've had the pleasure of watching the prosecutor get bitch slapped!
At the arraignment, instead of entering a plea, she filed a demurrer. That kind of motion tells the prosecutor, that his complaint failed to state a valid cause of action and even if it did, the facts alleged were insufficient to amount to a violation of that cause. (That's the equivalent of saying, yeah, my client committed those acts, so what?) And even if the demurrer is unsuccessful, you still get to see the prosecutions entire case presented before trial and you've also set the stage for a powerful appeal if you lose at trial.
I think a demurrer could work for Mr. Arford. If the facts outlined in the newspaper article are complete and accurate (that'd be a first!), Mr. Arford's action, in grabbing that rifle, never amounted to a violation of any law. Not only would it never go to trial, it won't even get past arraignment. And after a successful demurrer, judges tend to look very favorably upon any defense motions for return of property.
A demurrer is a very rare motion in criminal cases, maybe once in every 10,000 cases. Mostly that's because of ignorance on the part of lawyers. Many think it's only an option in civil cases. Others are unfamiliar how to draw up such a motion in a criminal case and how to use it as a pre-trial tactic. Another reason it's so rare is that the defendant can't avail himself of that motion after he has once entered his plea, and in many cases that happens before the lawyer gets involved.
Regards,
Boot Hill