Due to reports of cheating, Techland issued a patch that disables modification of game files by end users. Unfortunately, this has the side effect of disallowing all PC mods in their entirety.
Naturally, this sparked a bit of an uproar, and Techland responded by saying that they support the modding community and will be working on a fix that will reintroduce the ability to change certain common variables within the game while preventing cheating in multiplayer.
Children, this is why we can’t have nice things.
Thanks to Crave’s Game Revolution for the update on this story.