I don't know about other states, but, here in Ca it's not illegal to remove a VIN tag to do repairs. Having been in the automotive industry forever, one of the associations I used to belong to had a meeting with top DMV officials on the subject. He assured us that removing and replacing the VIN tag for a repair was not in violation if no fraud is involved. In fact, being a licensed auto dismantler, I was required to destroy VIN tags, or, certify that they would be destroyed by using only scrap metal recyclers that would also agree to destroy them. If we sold a part that had a VIN tag (like a dash frame, door pillar, etc) we were required to remove it and destroy it. Any other part with an etched, stamped, or tagged VIN and you had to note the VIN on the sales invoice.