Well, if they're going to arrest someone, they'd have a belief that they're a criminal. If there's evidence that they have a gun (e.g. entry in the gun registry under their name), then they'd have to consider it an attempt to apprehend a presumed-armed, suspected criminal.

I don't see why a registered gun would be a point in their favor. They probably registered their car, paid their taxes, and stopped at red lights too.