[MD Expat in PA]

In this usage, the comma was not a “serial comma” as you so ignorantly claim. The part of the sentence after the comma was a qualifier that applied to the first part.

The first part of the sentence said “who are foreigners, aliens,

The second part:

who belong to the families of ambassadors or foreign ministers accredited to the Government of the United States, but will include every other class of persons.

It does not say: who are foreigners, aliens, or who belong to the families of ambassadors or foreign ministers accredited to the Government of the United States…

It would be like saying: “I like my neighbors, the Amish who live near my house, who provide milk from their farm to my family at no cost.

In that sentence (yes awkwardly constructed but grammatically correct) you are not saying you like all your neighbors or all who live near your house who have a farm or even all you Amish neighbors, but only the Amish neighbors who live near your house who have a farm and who also provide you with free milk.

And you completely ignored and failed to address everything else I said. Congratulations for your witty repartee and your reading comprehension fail.

[MamaTexan]

In this usage, the comma was not a “serial comma” as you so ignorantly claim.

From the link:

The comma that precedes the conjunction before the final item in a series.

The sentence in question:

This will not, of course, include persons born in the United States who are foreigners, aliens, who belong to the families of ambassadors or foreign ministers accredited to the Government of the United States, but will include every other class of persons.

Three classes excluded
foreigners
aliens
diplomats and their families.

The final, and excluded classification is preceded by the CONJUNCTION 'but'
will include every other class of persons.

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I've shown you my proof, now you show me yours.