As it was described to me by someone who is close to the KS decision, registration was not part of the original sentence. It was added later. That's why the KS Supreme Court ruled it unconstitutional.
Registration after the fact is morally wrong, and in spite of the SCOTUS ruling, I think it is also unconstitutional.
I'd comment, but it was a 5-4 decision by the only qualified people to decide such a case, so I have to keep my unqualified mouth shut.