We gave them limited powers, and none of those extend to the bedroom.
Granted, so long as there is no harm to another person or their property and everyone has attained the age of majority. But even these rules can only be defined, imposed and enforced by the state or local governments.
If the Supremes are over-stepping their bounds, so is Mr. Santorum.
Conservatives trust "We the People" (i.e. a moral society), since "We the People" ARE supposed to be the government.