The service can disable their accounts (if any exist) and block their IP's; the service can stop doing any business with them if they don't like the ToS; but the service can ask them to comply, but can't really demand that they comply with ToS, it's not a law nor a contract that they've agreed to.
And the author is misdirecting the readers by providing a document not related to the claim he makes (TOS infringement vs «droit des marques» infringement).
EDIT/PS «nul ne peut se prévaloir de ses propres turpitudes» means that you cannot prevail your self of any wrongs if it is initially resulting from you not respecting the law. For instance if you build your company on a clearly fraudulent base (parasitism), you cannot claim for any reparation if you are shut down because it is a clear consequence of your actions. As a result, for the lawyer «faisceau de présomption valant preuve» his credibility in front of any juridiction would be voided.