27 C.F.R. § 479.52
Special tax stamps are merely receipts for the tax. Payment of tax under Federal law confers no privilege to act contrary to State law. One to whom a special tax stamp has been issued may still be punishable under a State law prohibiting or controlling the manufacture, possession or transfer of firearms. On the other hand, compliance with State law confers no immunity under Federal law. Persons who engage in the business of importing, manufacturing or dealing in firearms, in violation of the law of a State, are nevertheless required to pay special (occupational) tax as imposed under the internal revenue laws of the United States. For provisions relating to restrictive use of information furnished to comply with the provisions of this part see §479.23.
27 C.F.R. § 479.52