In the old days, when the plaintiff brought a civil rights case against the government or a private entity, he was considered the "prevailing party" if the defendant changed the very policy or rule that gave rise to the lawsuit. While the policy change may have mooted out the suit, if the policy change gave the plaintiff what he wanted in the first place, then the plaintiff was considered to have won the case and was therefore allowed to recover his legal fees from the defendant. We called that the "catalyst theory" of attorneys' fee liability.
The catalyst theory died in 2001, when the Supreme Court issued Buckhannon v. West Virginia, 532 U.S. 598 (2001), a sea change in attorneys' fees case law since most of the federal courts had adopted the catalyst theory. On the basis of its reasoning, courts have applied Buckhannon to every statute that allows for fee-shifting. One by one, these statutes are being narrowly interpreted under Buckhannon. You can now include the Equal Access to Justice Act in that category.
The case is Ma v. Chertoff, decided on November 4. This case involved the government's failure to allow the plaintiff to become a lawful permanent resident. Under the catalyst theory, if the plaintiff won, then his attorney recovered all legal fees expended in handling the case, which can be quite substantial. But the government gave in and granted Ma's application mid-litigation and gave him a green card. His lawyer moved for legal fees. Motion denied. Following the lead of other appeals courts which have ruled on this issue, the Court of Appeals holds that Buckhannon's reasoning applies to the fee statute governing these cases, the Equal Access to Justice Act. So the plaintiff wins the case, but his lawyer does not get paid.