On the international level, the law which circumscribes terrorism and provides sanctions for those who engage in terrorist acts is contained in a series of multilateral conventions. Several international instruments require the parties to establish criminal jurisdiction over specified offenses typically committed by terrorists and to make these offenses punishable by severe penalties. These conventions include the Hague Convention of 1970, which covers aircraft hijacking; the Montreal Convention of 1971, which applies to aircraft sabotage; the 1975 Convention on the Prevention and Punishment of Crimes Against Internationally Protected Persons; and the 1979 Convention Against the Taking of Hostages. In extradition treaties, there is a growing trend toward elimination of the political-offense exception to extradition as a shelter for fugitive terrorists. Currently pending before the Senate Foreign Relations Committee are six recently negotiated treaties on mutual assistance in criminal matters. There has also been informal law enforcement cooperation at the international level. Through the aforementioned efforts, the United States has sought to ensure that terrorists are tried, convicted, and imprisoned for their crimes.