The Tribal Police Department Parity Act seeks to establish equal access to firearms for Tribal law enforcement agencies, aligning their capabilities with those of Federal, State, and local counterparts. This legislation addresses existing disparities by amending key Federal statutes to explicitly include Indian Tribes in provisions related to firearm acquisition and use. Specifically, the bill modifies Title 18 of the United States Code to allow Indian Tribes, or their departments and agencies, to transfer, possess, and transport firearms, including certain machineguns, under the same conditions as other law enforcement bodies. Furthermore, it amends the Internal Revenue Code of 1986 to extend exemptions for firearm transfer and making taxes to Indian Tribes, ensuring they are not subject to taxes that other governmental law enforcement agencies are exempt from. These changes apply to firearms transferred or made after the act's enactment, thereby granting Tribal police departments the necessary legal framework to acquire essential equipment.