This week Valve seems to have quietly rolled out a new type of Steam game ban, "Banned By Developer", which can be applied by Valve when an approved developer flags a player who is cheating or otherwise mucking up their online multiplayer game.
That means game makers now have more control over Steam's ban system -- prior to this, Valve's Anti-Cheat System might ban players from playing game like Call of Duty online if it detected cheats, hacks or other troublesome game mods running on their PC during play, but not for more nebulous offenses like toxic behavior.
Now developers can implement their own standards for banning players (temporarily or permanently) and call in Valve to enforce those bans. Steam profiles will now also display which games a player has been permanently banned from playing online.
The move also places more responsibility on developers themselves, as "Banned by Developer" players are encouraged to first dispute their bans with the developer in question. If Valve perceives a developer to be abusing the system, it can in turn ban them from banning people.
This is in line with Valve's ongoing attempts to combat disruptive behavior on its platform, most recently evinced by its decision to restrict unfunded Steam accounts in order to cut down on spam and phishing scams. For more details, check out Valve's FAQ on the new system.