What is a violation of the us constitution if it was written into a state constitution

The Constitution is one source of law. When something is done in violation of the Constitution it is "unconstitutional". Legal vocabulary aside, that term means exactly what it says: contrary to the Constitution. Because the Constitution is a source of law, everything that is unconstitutional is also illegal.

Explanation:

No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing 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.