No, the federal courts have said that ex-post facto is a concept only in federal law.
I should have said "criminal law," not federal law.
They are mistaken.
Section 10. No state shall enter into any treaty, alliance, or confederation; grant letters of marque and reprisal; coin money; emit bills of credit; make anything but gold and silver coin a tender in payment of debts; pass any bill of attainder, ex post facto law, or law impairing the obligation of contracts, or grant any title of nobility.