It’s not clear to me that “jurisdiction” is being used in the same context in the 14th amendment as in Schooner Exchange.
Regardless, I wouldn’t call an argument supported by clear dicta in one Supreme Court case and a solid dissent in another “frivolous.” But I’d put the odds of the Supreme Court ruling in Trump’s favor substantially below 10%. You lose 100% of the shots you don’t take, though.
I feel we could usefully keep in mind another observation of Marshall's quoted in Wong Kim Ark, seperate from his writings in Schooner Exchange mentioned above:
"It is a maxim not to be disregarded that general expressions in every opinion are to be taken in connection with the case in which those expressions are used. If they go beyond the case, they may be respected, but ought not to control the judgment in a subsequent suit when the very point is presented for decision. The reason of this maxim is obvious. The question actually before the court* is investigated with care, and considered in its full extent. Other principles which may serve to illustrate it are considered in their relation to the case decided, but their possible bearing on all other cases is seldom completely investigated."
* The question in Slaughterhouse cases being on the topic of whether the 14th Amendment automatically subsumed the legislative authority of states in important respects, rather than the eligibility of children of foreign nationals for US citizenship.
Sure, maybe the Slaughterhouse Cases dicta was just wrong. But maybe there is something in the historical use of “jurisdiction” that sheds more light on what “subject to the jurisdiction” means. I haven’t done the deep dive myself, I’m just unpersuaded by the common law argument in Wong Kim Ark unless that really is all the historical record leaves us to go on.
Regardless, I wouldn’t call an argument supported by clear dicta in one Supreme Court case and a solid dissent in another “frivolous.” But I’d put the odds of the Supreme Court ruling in Trump’s favor substantially below 10%. You lose 100% of the shots you don’t take, though.