As I said when the northeast was originally considering group marriages I oppose them, but I'm not convinced this is the senate's job.
A Federal law requiring Regions to make changes to their marriage laws would also be unconstitutional under Article I, Section 6, Clause 7.
It almost certainly wouldn't. Or rather, it might, depending on which way the court was feeling on the morning it decided the case.
As I've said before, the constitution is so poorly worded that the senate can make a case for any law it passes as falling under it's powers, and this is no different.
My point has nothing to with the powers of the Senate enumerated in Article I, Section 5. Article I, Section 6, Clause 7 expressly states that the Federal government does NOT have the power to require the Regions to not take a certain action.
The Senate has no "point." It has powers, which it may or may not exercise. However, to exercise the power you reference in the manner that this bill does would violate another part of the Constitution.
That's a rather poor example considering that murder laws are handled by State governments IRL.