Lawsuits against the federal government can be dismissed under the doctrine of sovereign immunity. For example, Al Haramain Islamic Foundation v. Obama was recently dismissed (Appeals court dismisses warrantless wiretapping suit). The constitution refers to the "immunities of citizens" but not to "sovereign immunity".
Was federal sovereign immunity in place from the beginning? Was it established by a particular court ruling, or was it understood to be in effect (e.g., due to common law precedent)? Has there ever been a significant controversy over federal sovereign immunity?