SCOTUS is the last appeal if one challenges the validity a law.

[discntnt_irny_srcsm]

For a law to be valid in the US it must pass muster in comporting with the Constitution. There are other countries that operate under "Parliamentary sovereignty": https://en.wikipedia.org/wiki/Parliamentary_sovereignty

IMO parliamentary sovereignty is more Democratic than our system. Democracy in its pure form has also been criticized in the analogy of 'pure Democracy is 2 wolves and a sheep voting on what to eat' or something like that.