Well, how about this gem of info I found out? And one more time, the Senate and House were both controlled by the Democrat Party.
Remarks Upon Signing a Bill Restoring Rights of Citizenship to General Robert E. Lee, August 5, 1975
[General Lee's character has been an example to succeeding generations, making the restoration of his citizenship an event in which every American can take pride.]
Page:United States Statutes at Large Volume 89.djvu/440 - Wikisource, the free online library
What authority did the federal government have to revoke his citizenship in the first place?
None except force of arms. Like any totalitarian state. I dont think he really lost citizenship but only had his civil rights revoked. His pardon was misplaced until an archivist with the National Archives discovered it in 1970 misfiled.
Washington's actions were enough to scare the British colonies of North America into Confederation as they watched southern people conquered and forced into a Union they had desired to not be part of.
As a side note, Lee's house was also seized but years later the Supreme Court issued a rebuke for the seizure and paid the Lee family 150,000.