Originally Posted by ratbastid

Ideal world "should"s aside, the constitutionality of legislation is really honestly of only theoretical importance to a legislator. What's important to that legislator is how their support of the measure in question will make them look to their constituency. In principle, that's because they're elected to carry out the will of the people. In practice, their constituency includes deep-pocketed concerns like corporations and lobbying groups as well, so... Like the man says: Two things you DON'T want to watch people make are sausages and laws.

Constitutionality of the law is ruled on by the Supreme Court. That's one of the Court's key functions, and the main check on legislative power. I know the checks and balances structure is a little out of favor since our last Unitary Executive did away with it, but it still actually is the law of the land.