11.   But delivery was blocked by U.S. law forbidding military aid or sales to Pakistan unless the president certifies that country is not pursuing development of nuclear weapons.

12.   The certification program requires the U.S. president to certify annually whether countries that feed illegal drug markets in the United States are cooperating in anti-drug efforts.

13.   The law bars the United States from providing Islamabad with military or economic aid unless the U.S. president certifies Pakistan is not seeking to make atomic weapons.

14.   The president can certify North Korean compliance, waive the requirement or not certify.

15.   The Pressler Amendment requires an embargo of military supplies if the U.S. president cannot certify that a recipient country has no program to develop nuclear weapons.

16.   The sale was blocked by U.S. law forbidding military aid or sales to Pakistan unless the president certified that Islamabad was not pursuing development of nuclear weapons.

17.   The U.S. Foreign Assistance Act requires the president to certify each year which nations are cooperating with efforts to curb drug trafficking.

18.   Those listed face a cutoff of foreign aid unless the president certifies they are making a good-faith effort to combat the drug trade.

19.   Under U.S. law, the president must certify annually which states are cooperating in efforts to fight drug trafficking.

20.   The sale to Pakistan was held up under the Pressler amendment which requires the US president to certify that Pakistan does not possess nuclear weapons.