There is manual moderation, but server owners and/or moderators can hardly be online 24/7, and we need some (global) new anti-cheat system for that.
I don't really understand why CS2D still does not have VAC implemented, it is now on Steam and a multiplayer game, which qualifies for Valve's VAC usage requirements. Is it impossible to implement VAC into CS2D?
If it is because of CS2D's state as Counter-Strike replica that refrains it from getting VAC protected, I would like to suggest BattleEye as an alternative. It has been used by many games and is proved to be successful, at least protecting against loads of cheats.
If it is because implementing new anti-cheat methods require more works, I would like to emphasize that it is crucial to the game. This game already has limited online player base, if cheats go unattended, new players will definitely quit the game once they played against cheaters for a few games.
Sure, it is fine that you do not place a new anti-cheat system. But what of a global USGN ban system? Considering that the game already checks players' USGN on connection, adding a new data for verification shouldn't really consume much traffic. Some bit of code, and it is done.