For example the constitution lists (enumerates) specific powers of the federal gov't, rights of the people and leaves all else up to the several states to decide. To call a state law permitting specific folks to be married (or carry a gun) unconstitutional because it denies "equal protection" to other folks means that only the least restrictive state law (currently in existence?) is then constitutional.
Note that a constitutional amendment, rather than a SCOTUS "interpretation", was deemed required to give women (and then blacks) the right to vote. While gender and race are specifically mentioned in the constitution "gender preference" is not. While the 2A gives the people the right to keep and bear arms many state laws are allowed to separate (sever?) the "and bear" part into a need for CCW permits for handguns.