In regards to the 2nd Amendment, something the Democrats should seriously reconsider their disdain for, it can't be gutted by Congress as long as the checks and balances of the country function.

3/4ths of the states would have to agree to change a foundational pillar in the Bill of Rights.

In regards to some federal laws, they can be ignored within states when the federal government can't legitimately claim jurisdiction (cannabis grown, sold, and consumed within a state for instance).