I'm not defending their action, but there is a question of (a) authority and (b) capability. You're asking about authority, and yes SBF has stepped down, but the Bahamian regulator may have undertaken this on its own authority (possibly also with a judicial warrant, to perfect the authority), and so all they were lacking at that point was capability, which SBF could provide. It's sort of like if a criminal has a key to a shed with stolen goods in it -- we all agree the criminal does not legally own the goods, but he has the key, so you compel him to open it up.