That would be an interesting exercise. I suppose if it were outlawed the feds would seize all related domains and raid the HQ for Polymarket and Kalshi both in NY and freeze all their assets. It might spring up in another country under another domain name but then those could be seized as well. It could move to Tor but then money would have to be moved around on something like Monero I suppose. Anywhere money is involved gives countries incentives to cooperate.

Which countries would be best for them to operate out of if they were outlawed? What percentage of their user-base would use the Tor Browser?

Odd, I just noticed both Polymarket and Kalshi are hosted on the same IP address in San Fransisco. The IP belongs to Amazon but is not part of their cloud. That CIDR used to belong to Peer 1 Dedicated Hosting and then Aptum Technologies and now Amazon in SF. Kalshi used to be based out of SF but moved to NY.