Here’s how I expect it would work (putting all the onus on the employee):
All spousal coverage is cancelled until you provide your tax return showing no W-2s for your spouse the previous year.
If there are W-2s, you must provide an affadavit from that employer stating no medical coverage is provided.
Ah, ain’t that just grand. There’s other stuff I could add but don’t want to set off the Nora Sam Adam sirens.