When the Secretary of the Treasury believes a person has violated, is violating, or will violate this subchapter or a regulation prescribed or order issued under this subchapter, the Secretary may bring a civil action in the appropriate district court of the United States or appropriate United States court of a territory or possession of the United States to enjoin the violation or to enforce compliance with the subchapter, regulation, or order. An injunction or temporary restraining order shall be issued without bond.