By the Middle Ages the power of the Church was such that it was able to forbid Christian knights from using certain weapons as hateful to God. In fact, the feudal knights were aware of what they knew as 'the law of chivalry'. The 'law of chivalry' was a customary code of chivalrous conduct that controlled the knight's affairs, which was enforced by arbitrators specially appointed or, in England and France, by Courts of Chivalry. Contrary to the Geneva Law is the law concerning means and methods of conducting actual military operations in armed conflict. This is known as Hague Law, although it had its origin in a conference of fifteen European states called in Brussels at the invitation of Czar Alexander II of Russia. Another instrument that seems to have been applied as expressing accepted law, even though it never received a single ratification, is the Declaration of London.