> I imagine they'd be able to figure out some form of Chat Control that passed legal muster. Perhaps a reduced version of Chat Control, say, demanding secret key escrow, but only demanding data access/scans of those suspected of a crime rather than everyone.

Isn't that pretty much excatly how it is done in Russia, which was ruled by ECHR to be illegal[0]?

https://hudoc.echr.coe.int/fre#{%22itemid%22:[%22001-230854%...