When Alito says the "definition of marriage" under that kind of context it's clear that the definition is expository, falls clearly under the judicial discretion afforded to terms in common use, and is not a regulation. I know you've got an untenable position to defend, but please stop being outrageously silly or I'll have to stop discussing this with you.
"I consider the foundation of the Constitution as laid on this ground: That "all powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States or to the people." [X Amendment] To take a single step beyond the boundaries thus specifically drawn around the powers of Congress, is to take possession of a boundless field of power, no longer susceptible of any definition (emphasis added)." --Thomas Jefferson: National Bank Opinion, 1791.