Actually, he is exactly correct. The only way to change that is to amend the Constitution to make abortion a federal matter. And he has been consistent in his position concerning the 10th Amendment.
Which other unalienable rights do you think the states can alienate if they want?
We did. It’s called the 14th amendment, which gives all persons the right to life, liberty, and property. Have Congress define person as starting at conception, and there you go, states have to protect the rights of pre-natal children. This is the civil rights issue of our time.
Mind you, I support the right of states to secede. If a state does not like it, it can leave as far as I am concerned. I have no desire to cooperate with a state that allows the murder of some of its citizens. We obviously are not defending the same things.