Admiralty Grant

Justice Bradley, in later opinions, established that the source of Congressional power of amendment was the admiralty grant itself, as supplemented by the "second prong" of the necessary and proper clause. [In re Garnett, 141 U.S. 1 (1891). The second prong of the necessary and proper clause is the authorization to Congress to enact laws to carry into execution the powers vested in other departments of the Federal Government. See also Detroit Trust Co. v. The Thomas Barlum, 293 U.S. 21, 42 (1934).]

"...as the Constitution extends the judicial power of the United States to 'all cases of admiralty and maritime jurisdiction,' and as this jurisdiction is held to be exclusive, the power of legislation on the same subject must necessarily be in the national legislature and not in the state legislatures."

"It is unnecessary to invoke the power given the Congress to regulate commerce in order to find authority to pass the law in question. The act was passed in amendment of the maritime law of the country, and the power to make such amendments is coextensive with that law. It is not confined to the boundaries or class of subjects which limit and characterize the power to regulate commerce; but, in maritime matters, it extends to all matters and places to which the maritime law extends." [Butler v. Boston & S. S.S. Co., 130 U.S. 527 (1889).]

Notation from Kaiser Aetna v. United States, 444 U.S. 164 (1979):

[Footnote 7] Congress, pursuant to its authority under the Necessary and Proper Clause of Art. I to enact laws carrying into execution the powers vested in other departments of the Federal Government, has also been recognized as having the power to legislate with regard to matters concerning admiralty and maritime cases. Butler v. Boston S. S. Co., 130 U.S. 527, 557 (1889). See also, e. g., In re Garnett, 141 U.S. 1, 12 (1891).