Spokesman Joseph Zwilling said Monday that Egan was talking about Breyer's votes on the court in favor of abortion rights.
The protest against Breyer is being led by the Cardinal Newman Society, a Virginia-based conservative Catholic group.
Breyer is scheduled to receive the Fordham-Stein Ethics Prize Wednesday at a dinner in New York. Past recipients include state and federal judges who also support abortion rights.
More than 1,100 Fordham alumni and others have signed a petition to the university administration calling for the reward to be revoked, the Cardinal Newman Society said on its Web site.
The petition specifically cites Breyer's majority opinion in a 2000 case that struck down a Nebraska law banning a procedure that abortion opponents call partial-birth abortion as well as Breyer's dissent in a 2007 case that upheld a federal law banning the same procedure.
Breyer and the law school did not immediately respond to requests for comment Monday.
Egan has previously criticized Catholic elected officials and candidates who support abortion rights. Zwilling said this is the first instance he is aware of in which Egan has spoken out against giving an award to someone over the issue of abortion. In addition, Breyer is not himself Catholic; he is Jewish.