Why? Because it worked so well doing that with human slavery? No, wait. Maybe that didn't work out so well and it had to be done, first by decree (see the Emancipation Proclamation) and then by amending the Constitution.
Yes, wait. The alternative is for the United States to not exist. Most of our Founders detested slavery (even those who owned slaves). They permitted slavery to exist as a states' issue, even though slavery flew in the face of every principle on which our nation was founded. They did so because the people were too divided to come together as a union otherwise. Overturning Roe would be a huge step forward.
The fact is, it's going to be a state issue either way. How do you intend to get the HLA through without the states' assent?
Maybe that didn't work out so well and it had to be done, first by decree (see the Emancipation Proclamation) and then by amending the Constitution.
You skipped a step in there, namely a bloody and devouring civil war. Is that your proposal -- that the president issue a proclamation and then send in the troops?