If he’d used campaign funds or public funds....they’d have a case. Private funds? Unless he did some illegal wire transfer, or allocated the money into several transfers (all less than $10k each)...that’s about the only way to be in violation of the law. On the other side of this...it would be curious to know if Stormy reported it as taxable income to the IRS. She might be the only one getting into serious trouble.
And Donald Trump never signed the agreement. That was one of the reasons Daniels tried to get the agreement overturned. I wonder if she ever paid the money she owes President Trump for legal fees.