The government charged Davis with treason against the United States for organizing and arming the 1864 military invasions of Maryland and the District of Columbia during the American Civil War (1861–1865). The defendant demanded a trial as the best forum for proving the constitutionality of secession, and the government requested numerous delays to prepare its case. Although the indictment was finished in March 1868, the Johnson impeachment further delayed the case. The court finally heard preliminary motions in December 1868, when the defense asked for a dismissal claiming that the Fourteenth Amendment to the U.S. Constitution already punished Davis by preventing him from holding public office in the future and that further prosecution and punishment would violate the double jeopardy restriction of the Fifth Amendment. The court divided in its official opinion and certified the question to the United States Supreme Court. Fearing the court would rule in favor of Davis, Johnson released an amnesty proclamation on December 25, 1868, issuing a pardon to all persons who had participated in the rebellion.
Nonsense. Johnson had already issued two earlier amnesty proclamations not caring what the court might say. His December 1868 proclamation was a final middle-finger at the hardline Republicans who had dogged him his entire time in office.
Far from seeking trial, Davis employed lawyers who sought to prevent his trial. His attempts to legally justify not being subject to trial failed.
As a matter of mercy, his prosecution was dropped. After that, noone paid much attention to him, so he wrote his fiction on the ‘rise of the confederate government’ and the ‘fall of the confederate government’.
His return to popularity was based on his work as a fiction writer.
Texas A and M was lucky he didn’t accept a position there.