The Military Religious Freedom Foundation said Monday the suit has been filed in Denver federal court. The academy is in Colorado Springs, Colo.
The faculty members and the foundation are also asking for a preliminary injunction to block the event.
An academy spokesman didn't immediately return a call.
Retired Marine Lt. Clebe McClary is scheduled to speak at the event at the academy on Feb. 10.
McClary describes himself as a Christian motivational and inspirational speaker.
(Copyright 2011 by The Associated Press. All Rights Reserved.)