Guam and the United States disputed responsibility for environmental hazards at the Ordot Dump, which the Navy built and used before Guam operated it as a public landfill. After Guam entered a Clean Water Act consent decree with the Environmental Protection Agency, it sued the United States under the Comprehensive Environmental Response, Compensation, and Liability Act, seeking to pursue either cost recovery or contribution for cleanup expenses. The Supreme Court held that a settlement triggers a CERCLA contribution action only when it resolves a CERCLA-specific liability. The text and structure of the contribution provisions presuppose a CERCLA liability, and a settlement resolving environmental obligations under another statute does not become a CERCLA settlement merely because the remedial work overlaps. The Court rejected a broader reading that would allow a contribution action whenever a party settled any environmental liability. It reversed the D.C. Circuit and remanded for further proceedings.