I teach in a midsize Irish law faculty. Everyone in the department has some sort of regular administrative post. Mine is the department's director of research. As such, I spend some real quality time worrying (and conferring with colleagues) about (relative) journal and faculty metrics.
Many (perhaps most) American JDs -- current and former -- know about the Washington & Lee rankings for law journals. W&L's user friendly website is here: http://lawlib.wlu.edu/LJ/. W&L's rankings do not carry a lot of weight in Europe. Here the focus is more on peer reviewed law journals and journals which are cited in other peer reviewed journals. So European scholars interested in metrics look to the most recent reference of the Australia Research Council ("ARC") which ranked the "top" 1167 law journals worldwide. The ARC rankings were not limited to law; and ranked journals in a greater many fields. (You can find a copy of the most recent ARC rankings here: http://works.bepress.com/seth_barrett_tillman/237/ -- go to the bottom of the page.) The journals were not given individual rankings; rather, they were ranked in broad bands: A*, A, B, and C. The ARC rankings were last updated in 2010; so their continued relevance is capable of doubt.
Another ranking is Clarviate/InCites' (formerly Thomson Reuters') Journal Citation Reports (JCR). If you have access to Westlaw or other Thomson Reuters products, you may be able to see the JCR rankings for law (and other fields).
There is also Elsevier/SCOPUS/SCImago's Journal (and country) Rank indicator (“SJR”). As I understand it, the SJR rankings were designed especially to facilitate cross-border rankings among Europe's many linguistic groups and journals. (Scopus website: http://www.scimagojr.com/ -- it uses SJR rankings for law and other fields.)
Heads Up: If you are a law review editor, and you are not ranked by W&L, SJR and/or JCR, then you should apply for a ranking. It is free, and there is no downside (of which I am aware).
W&L, JCR, SJR, and HeinOnline are all current with 2016 (if not some 2017) data.
I only recently came across HeinOnline's ranking of the top-250 law authors. It is (I believe updated monthly. (http://home.heinonline.org/top_authors/) It includes all authors, even if not academics, even if retired -- or dead. It is an interesting list. I have permission from HeinOnline to reproduce their rankings.
Seth Barrett Tillman, Ranking Legal Authors (not just academics): HeinOnline's "ScholarRank’s Top 250 Authors" -- 2017 Data, New Reform Club (June 26, 2017, 10:14 AM), http://tinyurl.com/y9gp26w5