Hence "modulo legal gloss". Which includes such elements as effective counsel, unbiased jury selection, proper procedure, evidentiary rules, etc. Now let's look at your link....
Yeah. Biased jury selection.
The Sixth Amendment lays out most of what comprises due process:
the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence.
Also Art III Sec 2:
The Trial of all Crimes, except in Cases of Impeachment; shall be by Jury...
And again, the Virginia statute clearly fails XIV:
nor shall any State deprive any person of life, liberty, or property, without due process of law...
But piling on additional penalties, ex-post-facto, without hearing, isn't due process.
That's the substance of the dispute here.