The purpose of the Supreme Court, as it’s used here in this country at this time, is to determine whether or not legislation is constitutional or not. The same is true for lower federal courts as well. They’re supposed to take the Supreme Court’s rulings and apply them evenly across other cases, then judge on the constitutionality of new issues as they arise until SCOTUS rules differently.
However, as we’ve seen, it doesn’t necessarily work that way. Anti-gun judges have been ruling against the Second Amendment for decades, often ignoring the text of the amendment and inserting their own feelings and opinions, pretending those somehow carry more weight than “shall not be infringed.”
With the nomination of Amy Coney Barrett, we may finally see the end of some of this stuff. At least, in theory.