They'll need one. They might even "get away" with it using proper legal counsel.

Absolutely correct. But it is fraud upon the court if the divorce wasn't "real" and distributions from qualified plans are made. Insurance coverage is another area your employer might have a lot of interest.

There's the rub. It's not illegal to remarry, but the divorce has to be real.

Don't know yet. If what the company alleges is true, there's fraud, both against the plan and the employing company. That's a big deal. If not, then this is much ado about nothing. The empolyer has a high burden of proof on this one, but it sure looks like they have a great case.