1. No state shall...pass any bill...law impairing the obligation of contracts,
So the no fault divorce laws are invalid.
That may be a good point.
Usually a no fault divorce means that the two parties can negate or void the binding contract of marriage, usually bilaterally, to each other without stating that one of the parties is at fault for breach of contract.
For example, you do not have to prove cruelty or infidelity as the reason that the contract was breached and thus void.
A unilateral no fault dovorce may be a government infringement on contracts.