get all of those funds that user have or simply confiscate or whatsoever in related to that.
Going back about enforcing KYC then expect it would really be on that path knowing that these platforms are regulated or following a set of rules but actually it isnt on the situation where you as a user would be tied up
that tight into your neck since you do have the options to take.
Just like on the example on where Binance do give out 2BTC/day withdrawal without KYC is already a generous take unless if you are a whale then that wouldnt be enough.
Any transactions that do correlate or connect with fiat then you would really need to go with the process.