For anyone who doesn't know how this will work:
Assuming:
1) The Senate passes the Red Flag bill
2) Biden signs it into law
What happens is this:
3) Numerous lawsuits are filed challenging the new law on constitutional grounds.
4) Federal courts - likely more than one - issue injunctions freezing the enforcement of the new law while it's constitutionality is the subject of ongoing litigation.
5) Assuming a lower federal court is dumb enough to challenge the SCOTUS on the clear signal it just sent, the case will go up to SCOTUS who will rule the Red Flag law unconstitutional on multiple issues.