Does the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)¹ suspend the states' authority to enforce environmental laws at sites selected by the federal government for remedial action? The United States has taken that position to avoid compliance with state laws at federally owned hazardous waste sites. The issue recently came to a head before the Tenth Circuit Court of Appeals in a case concerning the U.S. Army's Rocky Mountain Arsenal (Arsenal), located near Denver, Colorado.² The court held that CERCLA does not preempt the states' rights to exercise independent authority to protect their citizens' health and welfare, and the environment. Because the U.S. Environmental Protection Agency (EPA) delegated its authority to enforce the Resource Conservation and Recovery Act (RCRA) to Colorado,³ the court ruled, the state "has the authority to enforce [RCRA] at the Arsenal, and '[a]ny action taken by [Colorado] … [has] the same force and effect as action taken by the [EPA]…."⁴