To make their life easier. Student submitted pieces, I am supposing, are much, MUCH less likely to be of acceptable quality for a reasonably-high quality journal. If 1 in 10 faculty articles is of publishable quality and 1 in 50 student articles is, then it would seem to make much more sense to spend more time analyzing faculty articles to determine the best fit than to risk missing out on the next great student submission. Note I wasn't a journal person myself, and have absolutely no idea if my empirical suppositions are in the right ballpark, but this strikes me as plausible.

What about concern over reputation? Perhaps the journal editors have the impression (and perhaps it's true) that law professors don't take student work as seriously as work by fellow professors. So they don't want to publish it, for fear their reputation will suffer among the community they care about, law professors.

It's not really a big question. It's just like the arxiv requiring someone to vouch for you: it's a minimum quality threshold. People without the credentials may be able to provide brilliant work, but for every genius there's something O(bazillion) people whose articles would be a waste of time to review, simply because they have not (yet) earned the right to be taken seriously the way a practitioner or professor has. The academic and publishing politics get laid ON TOP OF that framework.

Just throwing this out, but to what extent does the refusal to publish excellent student articles pressure the students capable of them into supplying the professors with help on theirs? Amounting to something close to permitting their work to be stolen, in order to get secondary credit for it in a good journal?

I suppose that would fall under corruption.

Hi Will,
I'm curious (for entirely selfish reasons) about whether these journals view submissions from doctoral students in other universities similarly (assuming that the doctoral students are doing relevant work). Do you have a sense of this?

Similar to Christopher M's comment above:

A reason that has been given at least once is that publishing a student-written piece as an article (no matter how brilliant) alongside articles written by professors will antagonize the professor-authors. Professors will be offended by seeing their work alongside the work of a mere student, and/or the journal will violate an implicit understanding with professor-authors that student work will be published separately as a note.

In my opinion, this kind of thinking hurts second-tier journals. They get so few high-quality submissions that they can't afford to turn away a quality piece for any reason, let alone for such speculative reasons as these.

I'm not sure where it falls in the hierarchy, but the Columbia Journal of Gender & Law publishes all pieces as Articles, regardless of whether written by professors, practitioners, judges or students. We get a ton of crap, but that's why we have submissions editors to weed that out and give us the stuff that's plausible to publish. However, this may be an effect of being a feminist law journal, committed to being democratic, non-hierarchical, etc. etc. -- no distinctions are drawn based on the author's background.