Clearly the federal government asserts a fair amount of control over marriage - See DOMA or Obergefell but beyond that, do you think congress couldn't pass a la

Clearly the federal government asserts a fair amount of control over marriage - See DOMA or Obergefell but beyond that, do you think congress couldn't pass a law creating a national marriage license? Or say a minimum marriage age? I wouldn't argue that the Federal government doesn't delegate a lot of things to the States - see Medicaid - but that's not the same thing as the States doing something only because they can do it.