In today’s ruling in Kerry v. Din, Justice Scalia (author of the lead opinion) and Justice Breyer (dissenting) seem to agree on one curious point: They both refer to the Magna Carta without using the definite article.
For example, Scalia writes, “The Due Process Clause has its origin in Magna Carta.” (This is one of four instances in which he writes of “Magna Carta” rather than “the Magna Carta.”) Likewise, Breyer: “It is that rule of law, stretching back at least 800 years to Magna Carta, which in major part the Due Process Clause seeks to protect.”
For what it’s worth, some quick (and non-exhaustive) research indicates that the justices have no consistent practice, either as a group or individually. Both Scalia and Breyer in previous opinions have referred to “the Magna Carta.” Justice Kennedy and Justice Thomas have also been on both sides at different times, with Kennedy using both forms within the same opinion. Chief Justice Roberts has so far (in at least two opinions) consistently declined to use the article.
I don’t know whether omitting the article is an Anglicism or a Latinism, but, for what it’s worth, I think that the omission sounds wrong in American English. The Magna Carta, after all, is a document, not a person.