On Jan. 30, Turkish authorities announced the freezing of more than half a billion dollars in assets owned by Veysel Sahin, who is accused of running illegal betting platforms and laundering criminal proceeds. An unidentified crypto company carried out the freeze at Turkey’s request, Istanbul’s chief prosecutor said. That company was Tether Holdings SA, issuer of the $185 billion stablecoin USDT — part of its recent push to aid governments around the world in crackdowns against crypto’s use in a...