They can’t re-establish the draft; Muhammad Ali defeated the draft in the courts and no individual that upholds their constitutional protections will ever again accept being drafted. Put simply, folks will just say no!
I'm no lawyer but I'm sure they'll come up with a law to bypass it somehow. The US is slipping into a banana republic. If the State wants warm bodies for a war, they'll get it. I would not be surprised if they attempt something similar to what Zelenskyy is doing right now; snatching people right off the streets.