The subject of bills of attainder is discussed in Public Safety or Bills of Attainder? — Written Jun. 14, 2000. Published in University of West Los Angeles Law Review, Vol. 34, 2002. This is to make some additional remarks on it and related subjects.
A question as arisen concerning Art. III, Sec. 2 Cl. 3 of the Constitution, which states “The Trial of all Crimes, except in Cases of Impeachment, shall be by Jury;”. That is not a delegation of a power. Powers to prosecute crimes are delegated elsewhere, in Art. I Sec. 1, Cl. 6, Cl. 10, Cl. 16, in Art. III Sec. 3 Cl. 2. and in Amendments 13, 14, 15, and 18 (repealed but with a lingering power in 21). The intent was not that it was only a right that could be waived by the defendant, as courts have held since, but also a mandate, since the Founders were well-acquainted with corrupt courts that could enter pleas or waivers without the consent of defendants.
So, yes, that means that every conviction of a crime in federal courts held without a jury is void.
The cited delegations of legislative powers are to adopt statutes to define what act is a crime, and the penalty for it. Congress may also legislate the creation of courts with various jurisdictions, including the jurisdiction to try cases in which a prosecutor petitions the court to find a defendant guilty of a legislated crime and apply the legislated penalty. The legislation defines the crime and declares a punishment for that crime, not for the offender, but the court applies the statute when it passes sentence, disabling the exercise of a right then depriving the disabled right, either permanently or for a period of time.
The delegations were for general categories of crime defined in the common law, but left it to the discretion of Congress to break out the general crimes into specific ones and to set the punishment for each. There are many things that can qualify as counterfeiting, piracy or felonies at sea, or offenses against the laws of nations, each with a different penalty. Treason, however, was defined, somewhat narrowly, in the Constitution, leaving to Congress only specification of the penalty for the various components of it (making war, giving aid and comfort).
Clause 16 is about discipline of military and militia, which includes criminal penalties.
The people are the sovereign, although they only act as sovereign when ratifying constitutions or constitutional amendments, either through legislatures or conventions.
The legislative disablement of a right to life, limb, or liberty, or punitive disablement of a right to property, is a punishment, even if actual deprivation is not immediately executed. It is authorizing others to execute deprivation, even if no specific warrants of execution are issued.
For more on this see Ex parte Garland , and the following quote, albeit from the dissenting opinion:
It is said that it is not necessary to a bill of attainder that the party to be affected should be named in the act …. It is very true that bills of attainder have been passed against persons by some description, when their names were unknown. But in such cases the law leaves nothing to be done to render its operation effectual, but to identify those persons. Their guilt, its nature, and its punishment are fixed by the statute, and only their personal identity remains to be made out.
A statute that declares a punishment for unnamed individuals who possess a firearm who are members of a class of those who are defined not by having had their right to do so specifically disabled by due process, but by other events or conditions, fits the above quote.