How much discretion should government agencies have to not make rules? Consider the following: In 1989, the Mine Safety and Health Administration (MSHA) proposed a comprehensive rule that would establish lists of hazardous substances: Permissible Expo- sure Limits (PELs) for more than 600 chemical substances that might be present in a mine, 165 of which would have been regulated for the first time.

While one phase of the rule was adopted after public hearings and comments in 1994, the MSHA withdrew the remainder of its rule in September 2002. Its primary reason was the "result of changes in agency priorities." The United Mine Workers union challenged the withdrawal of the proposed Air Quality Rule as arbitrary and capricious.

Find out what happened in International Union, United Mine Work- ers of America v. United States Department of Labor, 358 F. 3d 40 (D.C.Cir. 2004).