The case of U.S. v Dewitt, 76 U.S. 41 (1869) has been cited by Justice Thomas in his concurring opinion in U.S. v. Lopez (1995) as an example of federal legislation that was determined to be in the nature of "police powers" (protection of public health, peace, safety or morals;) therefore, held to be applicable only in Washington D.C. and the "territories" where Congress has "exclusive legislative jurisdiction." The Chief Justice in the Dewitt case stated:

"The questions certified resolve themselves into this: Has Congress power, under the Constitution, to prohibit trade within the limits of a State?

"That Congress has power to regulate commerce with foreign nations and among the several States, and with the Indian tribes, the Constitution expressly declares. But this express grant of power to regulate commerce among the States has always been understood as limited by its terms; and as a virtual denial of any power to interfere with the internal trade and business of the separate States; except, indeed, as a necessary and proper means for carrying into execution some other power expressly granted or vested."

"Standing by itself, it is plainly a regulation of police; and that it was so considered, if not by the Congress which enacted, it, certainly by the succeeding Congress, may be inferred from the circumstance...

"...As a police regulation, relating exclusively to the internal trade of the State, it can only have effect where the legislative authority of Congress excludes, territorially, all State legislation, as for example, in the District of Columbia. Within State limits, it can have no constitutional operation. This has been so frequently declared by this court, results so obviously from the terms of the Constitution, and has been so fully explained and supported on former occasions, that we think it unnecessary to enter again upon the discussion. [License Cases, 5 Howard, 504; Passenger Cases, 7 Id. 283; License Tax Cases, 5 Wallace, 470.]