Mr. Trumbull, from the committee of conference on the disagreeing votes of the two houses on the bill (H. R. 591) to indemnify the President and other persons for suspending the privilege of the writ of habeas corpus, and acts done in pursuance thereof, submitted the following report: .... [Emphasis added]
Which they had to know was immediately in contravention of existing law:
ARTICLE 1.
SECTION 9.
..... No Bill of Attainder or ex post facto Law shall be passed.
Please pardon the delay.
I must disagree that the action of Congress, granting Lincoln and subordinates indemnity from prosecution for prior actions relating the suspension of habeas corpus was an ex post facto law. This act did not actually retroact, but gave a prospective legal defense against civil or criminal prosecution for acts taken. The ex post facto clause applies only to criminal law, and only when it retroactively criminalizes an act, or retroactively increases the possible punishment for what had already been a crime.
What such a law does do is enable government officials to violate the guaranteed Constitutional rights of citizens and be shielded from any punishment. It is not clear that there is any Constitutional violation at all. The Constitution does not mandate any punishment.
This is not to say I like it, but I do not see a Constitutional violation. In fact, it appears similar to the Feres doctrine of today. Under Feres, if one is an active duty military member, one may not sue for injury, including medical malpractice, incident to service. This has been interpreted to become increasingly expansive in definition. One example would be if the service member underwent surgery for an ingrown toenail and, by mistake, they amputated his or her leg. A lawsuit for damages is barred by the Feres doctrine. This doctrine does not apply to a civilian dependent of the servicemember seen by the same doctor in the same military hospital.
Below is William Rawle's interpretation of ex post facto and a more recent commentary on Calder v. Bull.
A View of the Constitution, by William Rawle, 2 Ed., 1829, Chapter 10: "Of the Restrictions on the Powers of Congress — and on the Executive and Judicial Authorities — Restrictions on the Powers of States, and Security to the Rights of Individuals"
No bill of attainder, nor ex post facto law shall be passed.
Bills of attainder are those by which a person without a judicial trial, is declared by the legislature to be guilty of some particular crime. The definition itself shows the atrocity of the act. Such laws are never passed but in times of wild commotion or arbitrary misrule.
Ex post facto laws are often supposed to signify all laws having a retrospective operation, but the technical meaning of them is more confined. An ex post facto law is when an action is declared to be a crime, which at the time it was done was innocent, or when it aggravates a crime, and declares it to be greater than it was when committed, or when it increases the punishment, or directs that different or less evidence shall be sufficient to convict the offender; but if it softens the rigour of the ancient law, it is not within the prohibition.2 The Constitution does not prevent congress from passing retrospective laws in civil cases. Why this was omitted when the states in the same instrument are restrained from passing laws impairing the obligations of contracts, will be hereafter explained.
Citing Calder v. Bull, 3 Dallas, 386 (1798)
At the link:
Commentary on Calder v. Bull
Calder v. Bull is a seminal case concerning both the source of individual rights, and the ability of the Supreme Court to ascertain the content and protections afforded by these rights. This case was decided before Chief Justice John Marshall was appointed to the Court in 1801. Thus, the Court followed the English practice of seriatim (individual, serial) opinions. Marshall would change that practice by initiating the "opinion of the Court." The holding of Calder remains good law: the ex post facto provision of the Constitution (Art. I, § 10, cl.1) applies solely to criminal cases, not civil cases. For Samuel Chase, later impeached by the House (but acquitted by the Senate), the government has no authority to interfere with an individual's rights, and "the general principles of law and reason" forbid the legislature from doing so. For James Iredell, "[t]he ideas of natural justice are regulated by no fixed standard: the ablest and the purest men have differed upon the subject; and all that the Court could properly say, in such an event, would be, that the Legislature (possessed of an equal right of opinion) had passed an act which, in the opinion of the judges, was inconsistent with the abstract principles of natural justice." Iredell is skeptical about both the existence of natural rights, and the ability of the judiciary to assess accurately the content of those rights. Throughout American constitutional history, there has been skepticism about natural rights. For example, Justice Oliver Wendell Holmes was a complete natural rights skeptic. By the time of the constitutional crisis of 1937, a majority of the Court was convinced that natural rights talk was part of what came to be called "Lochnerizing," after the Lochner case. Thus, natural rights arguments were largely dismissed after 1937. But the Court has never abandoned claims to find unenumerated or implicit rights, as the "right to privacy" as developed in Griswold v. Connecticut (1965) and Roe v. Wade (1973) make clear. The controversy over Roe re-kindled a long existing skepticism about courts, and their ability to ascertain rights correctly. In the late 18th century, of course, more people were comfortable with the notion of natural rights than are people in the early 21st century.