All Senators and Congressmen take an oath to uphold the Constitution.

[kentuck]

That means if they allow Donald Trump to ignore the Constitution, they are breaking their oath to defend and protect the Constitution of the US.

Why is that important?

[atreides1]

1. Words, nothing but words!!!

The oath is meaningless to those who are only interested in power...it's just a ritual they have to perform in order to look legitimate!

The same goes for the flag and the anthem, a piece of multicolored cloth and a song that have little meaning to people who want power for the sake of controlling others!!!

[J_William_Ryan]

2. Its not quite that simple.

The doctrine of presumed constitutionality maintains that an act by Congress or the president is considered to be Constitutional until the Supreme Court rules otherwise (see, e.g, US v Morrison).

However, if Trump were to instruct Federal agencies to again enforce Section 3 of DOMA, for example, denying same-sex married couples access to Federal benefits, then Trump would be acting in violation of the Constitution, where it would be the responsibility of the courts, not Congress, to check the Executive’s un-Constitutional act pursuant to US v Windsor.

The problem, of course, is that most Congressional Republicans have as much contempt for the Constitution and its case law as Trump.