P operates care homes that provide assisted living to their residents. P failed an inspection by the West Virginia Office of the State Fire Marshal because some of the residents were incapable of 'self-preservation' as defined under state law. P sued on behalf of itself and other similarly situated homes and residents (hereinafter petitioners), brought suit in the District Court against the State of West Virginia (D), two of its agencies, and 18 individuals, seeking declaratory and injunctive relief in that the 'self-preservation' requirement violated the Fair Housing Amendments Act of 1988 (FHAA) and the Americans with Disabilities Act of 1990 (ADA). In 1998, the West Virginia Legislature enacted two bills eliminating the 'self-preservation' requirement. Ds moved to dismiss the case as moot. The District Court granted the motion, finding that the 1998 legislation had eliminated the allegedly offensive provisions and that there was no indication that the West Virginia Legislature would repeal the amendments. Ps requested attorney's fees as the 'prevailing party' under the FHAA, 42 U. S. C. §3613(c)(2) and ADA, 42 U. S. C. §12205 wherein the court in its discretion may allow a prevailing party ... a reasonable attorney's fee, including litigation expenses, and costs.' Ps argued that they were entitled to attorney's fees under the 'catalyst theory,' which posits that a plaintiff is a 'prevailing party' if it achieves the desired result because the lawsuit brought about a voluntary change in the defendant's conduct. The Court of Appeals for the Fourth Circuit rejected catalyst theory. The District Court accordingly denied the motion and, for the same reason, the Court of Appeals affirmed in an unpublished, per curiam opinion. The Supreme Court granted certiorari.