As Cinema Blend reports, the VZBV argues that users are coerced into agreeing to the updated EULA, because if they don't they lose access to their Steam accounts. The VZBV also wants Valve to enforce the European Court of Justice's ruling made in July, which states that authors cannot oppose their 'used' digital download software being resold.
Cinema Blend notes a suspicion that Steam's updated EULA is designed to protect Valve from class-action lawsuits related to the EU ruling. The VZBV originally gave Valve until September 26 (today) to respond to its desist order, but the organization later extended the ultimatum to October 10. We've reached out to Valve for comment.