Yes, say the authors of this article that surveys citation rates.
The stronger impact on citation levels comes from having an abstract, but tables of contents also contribute, and the two together generate citation rates 70% higher than articles without either.
Their theory is that abstracts and tables of contents reduce cognitive burdens on other researchers, which makes sense.
They don't appear to correct for article length, which might also be part of it, as my unscientific guess would be that long, 'battleship' articles of the type that might merit citations seem more likely to get the abstract and table of contents treatment. I also wonder whether some law reviews that generate high levels of citations are more likely to suggest/require both.
It doesn't take an empirical study to know that an abstract and table of contents are worth including. They're courtesies to readers, and that ought to suffice.
I agree about the abstract, not so sure that every article should have a table of contents. If it's a forty plus pager, including a TOC makes sense. I've seen 15 to 25 page submissions with one, though, which just seems silly.
Considering Word and other editing programs now make creating a Table of Contents automatic given your headings, there doesn't seem to be any reason not to include one. If the editors choose to take it out for space / formatting / consistency, so be it, but it isn't any extra work. It also often helps me see the structure of my own work better.
It is pretty rare to see a Table of Contents in other disciplines and their presence in Law Reviews is really just a sign that the articles are way too long. Books have Table of Contents, articles don't. Abstracts obviously make sense but sometimes they are as long as an article would be, again a function of trying to draw the uninformed Law Review editor in.