This excerpt taken from the ATVI 10-Q filed Feb 8, 2006.
Protection of Licensed Trademarks. Publisher shall assist Microsoft in protecting and maintaining Microsofts rights in the Licensed Trademarks, including preparation and execution of documents necessary to register theLicensed Trademarks or record this Agreement, and giving immediate notice to Microsoft of potential infringement of the Licensed Trademarks. Microsoft shall have the sole right to and in its sole discretion may, commence, prosecute or defend, and control any action concerning the Licensed Trademarks, either in its own name or by joining Publisher as a party thereto. Publisher shall not during the term of this Agreement contest the validity of, by act or omission jeopardize, or take any action inconsistent with, Microsofts rights or goodwill in the Licensed Trademarks in any country, including attempted registrationof any Licensed Trademark, or use or attempted registration of any mark confusingly similar thereto.