Let me spell this out for you, the process to repeal it is identical to the one used to pass it:
1) Repeal it in the House
2) Repeal it in the Senate, full repeal 60 votes, partial repeal 50 votes +VP
3) get the POTUS to sign the common bill
That is how it was passed, that is how it is repealed.
DUHH!
My original question asked how could it be constitutional?
I believe my question was answered in Post #30.
Once Post #30 is taken into account, then I can see the process as you outlined it (and I knew it to be for "normal" laws).
Thank you.