You can't force a private entity to sue another private entity. The regulator (government) can sue it if it finds it at fault. And a private entity can choose t

You can't force a private entity to sue another private entity. The regulator (government) can sue it if it finds it at fault. And a private entity can choose to complain to the regulator if it wants. The agreement here between MSFT and GOOG is to try and resolve disputes internally if possible without suing each other or complaining to the regulator. There's nothing illegal in that.