According to German Patent Law the courts are bound by the grant of a patent by the respective Patent Office. In consequence thereof they cannot hold a patent as null and void: an action for declaration of non-infringement cannot be based on the lack of patentability of the patent. However, a defence against an infringement action is possible by pleading that according to the state of the art the infringing object is covered by that state of the art or an obvious derivation of it and therefore cannot fall under the scope of the patent if that patent (the claims) would otherwise be infringed only in an equivalent way. But such a defence is consequently denied if the claims would be infringed literally – because then that defence based on prior art is equivalent to a claim of nullity of a patent which the courts are not allowed to judge due to the concept of bifurcation. This sort of defence, namely that the infringing object is made according to prior art, is called in Germany Formsteineinwand after a decision of the German Supreme Court ruling on such a defence.