I believe that the test to determine what a "fundamental right" is, is well established and now that fundamental status has been declared for the right to arms for self defense it can't be undone.
That all that judicial invention of standard of scrutiny exists, (along with selective incorporation), is why many people were so excited when SCOTUS granted cert to
McDonald v Chicago and not
NRA v Chicago (although they were joined later).
Conservatives and Liberals hoped that
McDonald's primary argument that the right to arms is enforceable on the states by way of the 14th Amendment's "privileges or immunities" clause, meant the Court would revisit
Slaughterhouse.
Slaughterhouse gutted the "privileges or immunities" clause which only left "due process' as the vehicle to apply the Bill of Rights to the states under the 14th Amendment. This also left unenumerated rights out in the cold, hence the "invention" of prenumbral rights including the right to privacy /
Roe v Wade.
"Due process" demands a case by case, fact by fact inspection which of course leaves politically agenda driven judges and Justices plenty of parchment to add to the Constitution.
Thomas' concurrence in McDonald is a history lesson and an explanation and indictment of the "legal fiction" described above.
Thomas's concurrence is a blueprint of where we
should be and I recommend everyone read it.
Liberals would be happy because the unenumerated rights they embrace would be secure without questionable reasoning and conservatives (at least those who cherish the Constitution, as opposed to "social' and "cultural" conservatives) would be happy because the Constitution would finally be enforced.