reasons for such discharges were not always made clear nor followed by formal prosecutions, and claimed that Pastrana's administration cut funds for the Attorney General's Human Rights Unit. Leahy Provision In 1997 the US Congress approved an Amendment to the Foreign Operations Appropriations Act which banned the US from giving anti-narcotics aid to any foreign military unit whose members have violated human rights. The Amendment was called the "Leahy Provision" or "Leahy Law" (named after Senator Patrick Leahy who proposed it). Partially due to this measure and the reasoning behind it, anti-narcotics aid was initially only provided to Police units, and not to the military during much of the 1990s. According to author Grace Livingstone and other critics, the problem is there have been very few military units free of members that have not been implicated in any kind of human rights abuses at all, so they consider that the policy has been usually ignored, downplayed or occasionally implemented in a patchy way. In 2000, Human Rights Watch, together with several Colombian human rights investigators, published a study in which it concluded that half of Colombia's eighteen brigade-level army units had extensive links to paramilitaries at the time, citing numerous cases which directly or indirectly implicated army personnel. The State Department certified that Colombia would have complied with one of the human rights conditions (Sec. 3201) attached to Plan Colombia aid, due to President Pastrana's directing "in writing that Colombian Armed Forces personnel who are credibly alleged to have committed gross violations of human rights will be brought to justice in Colombia's civilian courts...". In August 2000 President Clinton used his presidential waiver to override the remaining human rights conditions, on the grounds that it was necessary for the interests of U.S. national security. Livingstone argues that if the US government funds military units guilty of human rights abuses, it is acting illegally. Aerial eradication strategy and criticisms Aerial eradication (often incorrectly called "fumigation") began as a part of Plan Colombia backed by the United States government as a strategy to eliminate drug crops in Colombia in the 1980s. By the mid-1990s, drug cultivation had increased and Colombia supplied as much as 90% of the world's cocaine, which caused aerial eradication efforts to become more intensified. United States policymakers put the intensive use of the herbicide Roundup Ultra made by Monsanto for massive aerial spraying of illicit crops in Colombia