49 U.S.C. § 24306: Mail, express, and auto-ferry transportation

(a) Actions To Increase Revenues.—Amtrak shall take necessary action to increase its revenues from the transportation of mail and express. To increase its revenues, Amtrak may provide auto-ferry transportation as part of the basic passenger transportation authorized by this part. (b) Authority of Others To Provide Auto-Ferry Transportation.—State and local laws and regulations that impair the provision of auto-ferry transportation do not apply to Amtrak or a rail carrier providing auto-ferry transportation. A rail carrier may not refuse to participate with Amtrak in providing auto-ferry transportation because a State or local law or regulation makes the transportation unlawful.