Yes, for everyone except Davis.
So, technically, the traitors did not commit treason.
Robert E Lee’s US citizenship was not restored until 1975, by an act of Congress.
No they were just pardoned for their treason. That didn't change the fact they has committed it.
technically, the traitors did not commit treason
Legally, the Confederate soldiers were neither traitors, nor capable of committing treason. They fought for a recognized belligerent power.
Lincoln proclaimed the international act of a blockade. (The equivalent domestic act is a closing of the ports. On April 11, 1865, days before his death, Lincoln proclaimed the blockaded ports to be closed.) The international community responded to the proclmation of a blockade with a chorus of declarations of neutrality. By definition, a declaration of neutrality applies to the relations of the declaring state relative to two or more other recognized powers. In this case, the two states were the USA and the CSA.
Per the U.S. Supreme Court, the war started with President Lincoln's proclamation of a blockade.
The precise dates, and the precise events, of the start and end of the civil war was addressed by the United States Supreme Court in the case of The Protector, 79 U.S. 700 (1870).
It is necessary, therefore, to refer to some public act of the political departments of the government to fix the dates, and, for obvious reasons, those of the executive department which may be and in fact was, at the commencement of hostilities, obliged to act during the recess of Congress, must be taken.The proclamation of intended blockade by the President may therefore be assumed as marking the first of these dates, and the proclamation that the war had closed as marking the second. But the war did not begin or close at the same time in all the states. There were two proclamations of intended blockade: the first of the 19th of April, 1861, embracing the States of South Carolina, Georgia, Alabama, Florida, Mississippi, Louisiana, and Texas; the second of the 27th of April, 1861, embracing the States of Virginia and North Carolina; and there were two proclamations declaring that the war had closed, one issued on the 2d of April, 1866, embracing the States of Virginia, North Carolina, South Carolina, Georgia, Florida, Mississippi, Tennessee, Alabama, Louisiana, and Arkansas, and the other issued on the 20th of August, 1866, embracing the State of Texas.
The declaration of blockade on April 19th marked the beginning of the war for all legal purposes, and also established the Confederate States of America as a lawful belligerent power, meaning captured troops then enjoyed the right of prisoners of war.