The states do not have power to create or enforce any admiralty or maritime rule that conflicts with federal law, either directly or indirectly.  Since the Constitution has granted admiralty jurisdiction to the federal courts, a state statute or ruling of a state court shall not override the law of admiralty.  Moreover, since Congressional power in admiralty matters is non delegable, Congress cannot transfer such power. 

The paramount power of Congress excludes interference by state legislation with its exercise.  When a particular maritime subject is national in character, only Congress can legislate.  However, the states have the power to make laws so long as their legislation does not conflict with the valid federal legislation and does not interfere with the proper harmony or uniformity of federal law in its international and interstate operation.[i]  Therefore, states have authority to regulate issues such as navigation and mooring in their harbors and adjacent waters, matters such as liens for claims arising from repairs of vessels within the ports of the state, port regulations and safety in local harbors, and torts committed by vessels within such ports.

Although a state law cannot give jurisdiction to a federal court, a right given by state law can be enforced in the proper federal tribunal.  The federal courts have to decide how far state statutes may be taken up and applied to matters within admiralty jurisdiction. 

[i] Clark v. Cahill Bros., 67 Cal. App. 2d 689 (Cal. App. 1945)