Okay, legal eagles, prepare to be shocked. This is a little exercise in fantasy legal-land for my education.
To begin with, what would happen if some state actually did enforce a law flatly at odds with Roe v. Wade, Doe v. Bolton, and all the rest? You can parse out the exact details of the hypothetical state law here in a number of ways. Rather than take time to do that, I'll just say that we should surmise that at the end of the process--in which the executive, judicial, and legislative branches of the state all had to cooperate--some abortionist has been tried, sentenced, and is in jail for performing an abortion that Roe and company "don't allow" states to prohibit.
What happens? Well, obviously, at some point along the way the abortionist's lawyers bring suit in federal court, and I think we can assume that the federal court issues a court order to the state to release him. Suppose the state officials refuse. What then?
I'm guessing (but this is one place where I'll accept well-supported correction) that the federal court orders federal marshals to go to the state and enforce the court order that he be released. Correct?
If that's correct, then try this question out for size: What would happen if, at that point, the President of the United States ordered the federal marshals not to go? After all, enforcement powers are supposed to lie with the executive branch, are they not? It's not as though the judicial branch just has a standing array of guns at its direct disposal, is it? Would it or would it not lie within the powers of the President to order that no such court order be enforced? If the court doesn't order the marshals to go but expects the President to do so, then things are even easier. He can just refuse to do so.
Wouldn't it be interesting if a candidate for the Presidency promised to do one or the other of these and, in effect, to nullify Roe v. Wade by refusing the power for its enforcement against the state?
Probably you don't like that idea. Probably even some of my more conservative commentators don't like that idea. Okay, how about this one, which would require more people to be involved. Congress controls expenditures. What if Congress wrote into a budget bill an express provision that no funds could be used to enforce any federal court orders to states to release any abortionist from jail? Presumably the federal courts would declare such a bill unconstitutional, but what if Congress ignored that and refused to pass a new bill taking out that language?
Just a few, shall we say, creative thoughts on overturning Roe from the federal level, but without passing a constitutional amendment.