I don't think Etsy will monitor. They will probably be able to treat it like they do with taxes and health code compliance for foods sold - they will make it clear that each shop owner must be in compliance with whatever governmental rules are relevant.
Etsy is not buying our goods, is not the manufacturer, middleman, or final destination. Essentially Etsy is renting us space, with our rent being a percentage of our sales. Our listing fee is basically a charge for advertising. It would be impossible for Etsy to monitor our compliance. Bringing the point further, Etsy has shops whose owners reside outside the U.S., and if they sell to buyers in other non-US markets, than this doesn't affect them in the least.
I could see Etsy having all shop owners read and "sign" something saying that they are aware and agree to operate to the letter of the law.