I'm only saying that because it is also the Constitution that determines how the powers are divided among the branches and what limits are on those powers.
It is possible for the legislature to adopt rules or parliamentary procedure that would in itself be unconstitutional. The Supreme Court would have to be the one to rein that in because the legislative branch will not do that for itself.
Usually it's the Supreme Court through judicial review. The President ideally would not sign a bill into law when he thinks the procedure to get it to his desk was unconstitutional. That's not going to happen here.
The branches by design do keep an eye on each other with regard to the constitutionality of their actions.
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