"[I]f a man sues the government for wrongful detention, and if it is proven or conceded that he was at least detained, then the onus is on the government to show cause for his detention. If the government instead requests dismissal of proceedings [on the ground that litigation would expose state secrets], it has simply failed to show the necessary cause..."

Full article:  http://grputland.blogspot.com/2007/03/secrets-about-state-secrets-privilege.html