Francis A. Keating II, selected for the No. 3 job at the Justice Department, is a former FBI agent who has spent much of his time in the Reagan administration going after big banks who launder money for drug smugglers and other criminals. Keating, assistant Treasury secretary for enforcement, pursued various cases against banks for neglecting, either intentionally or inadvertently, a 17-year-old law requiring that the institutions to inform the government in writing whenever they handle a cash transaction of $10,000 or more. The Treasury crackdown assessed multimillion-dollar penalties against some of the nation's biggest banks, including a record $4.75 million fine paid by the Bank of America. The crackdown on money laundering was started by Keating's predecessor in the job, John M. Walker Jr., who is now a federal judge in New York, but Keating continued the effort when he took over at the Treasury Department in December 1985. As head of enforcement, Keating, 44, oversees the Secret Service, the Customs Service and the Bureau of Alcohol, Tobacco and Firearms. Keating was one of the officials charged with implementing the administration's stepped-up efforts at halting the flow of illegal drugs into the country. Keating, who will replace Associate Attorney General Stephen Trott, was praised by Attorney General Edwin Meese III as someone who ``can hit the ground running'' in the Justice Department's work in combating illegal drugs. Trott is leaving Washington to become a federal appeals court judge in California. At Treasury, Keating also has headed the Office of Foreign Assets Control, the agency charged with implementing economic sanctions imposed against Cuba, Libya, Iran and South Africa. Before joining the administration, Keating was a partner in an Oklahoma law firm. He also served as a U.S. attorney from 1981 to 1983 for the Northern District of Oklahoma. From 1972 to 1981, Keating was a member of the Oklahoma legislature, starting out in the House of Representatives and then winning a seat in the state Senate, where he served as Republican leader. Keating is also a former state prosecutor and FBI agent. He graduated from Georgetown University in Washington in 1966 and received his law degree from the University of Oklahoma in 1969.