(1) A defendant may apply by way of counterclaim in infringement proceedings an infringement proceeding for revocation of the patent on any of the grounds stated in section 106.
(2) If the defendant is a government department, it may apply by way of counterclaim in infringement proceedings an infringement proceeding for revocation of the patent on the ground stated in section 108 (whether or not it also applies by way of counterclaim for revocation of the patent on any of the grounds stated in section 106).