It is the purpose of this chapter to— (1) authorize and develop a comprehensive, coordinated attack upon the illegal narcotics traffic in Indian country and the deleterious impact of alcohol and substance abuse upon Indian tribes and their members, (2) provide needed direction and guidance to those Federal agencies responsible for Indian programs to identify and focus existing programs and resources, including those made available by this chapter, upon this problem, (3) provide authority and opportunities for Indian tribes to develop and implement a coordinated program for the prevention and treatment of alcohol and substance abuse at the local level, and (4) to [1] modify or supplement existing programs and authorities in the areas of education, family and social services, law enforcement and judicial services, and health services to further the purposes of this chapter. ( Pub. L. 99–570, title IV, § 4203 , Oct. 27, 1986 , 100 Stat. 3207–138 .)