MOVING TO FRONT FROM FEBRUARY 6, 2006, SINCE I STILL GET INQUIRIES ABOUT THIS.
Students, academics, and law schools themselves often talk in terms of schools being "national" or "regional," though there doesn't seem to be an agreed-upon set of criteria at work in such discussions. The vast majority of ABA-approved law schools are "national," for example, in offering a curriculum that is not specific to the state jurisdiction in which the school is located, so in terms of course offerings, "national" is the norm. More interesting to prospective students, and more likely what is at stake when students wonder whether a school is "national," are the employment prospects of graduates. Genuinely "national" law schools draw prospective employers to campus from around the nation, not just from the immediate area in which the school is located; more "regional" law schools mainly draw employers to campus from the immediate region. (The best advice for students is: ask to see a list of employers recruiting on campus--that will tell you more about employment prospects, and the "national" reach of the degree, than just about anything else.)
Data from the National Association for Law Placement on the number of firms interviewing on campus (and reprinted in the September National Jurist) gives some picture about which schools are "national" and which "regional", though the data is very crude for a variety of reasons: (1) it tells us nothing about how many positions each firm is looking to fill (a typical large Texas firm, for example, will often be prepared to hire a half-dozen or more UT grads in a given year); (2) it tells us nothing about the caliber of the firms interviewing on campus; and (3) employers have a variety of reasons for interviewing at a school apart from the quality of the legal education--for example: the school is near the firm's offices (a boon for schools in cities like New York and D.C. with huge numbers of law firms); the firm has been successful in recruiting students from the school in the past; size of the school (the more students, the more likely an employer is to land a graduate); affirmative action considerations; and so on.
Although Duke has more firms coming to campus than Yale according to the NALP data, this surely isn't because anyone is in doubt about the relative merits of these schools, but because many employers find they stand no chance of getting Yale grads, who are being sought after by the most attractive/lucrative employers in the nation. That more firms go to Virginia than Columbia surely has far more to do with the fact that Columbia grads overwhelmingly stay in New York City, where there are a multitude of attractive practice opportunities, whereas most Virginia grads leave the area, since none of the local markets compare to New York or Washington, D.C. or Los Angeles.
Given the limits of this information, noted above, I've listed the schools in broad categories based on the number of firms interviewing on campus according to NALP:
Over 800 firms: Georgetown, Harvard [note, of course, that Georgetown and Harvard are the two largest top law schools in the country in terms of student population]
Over 700 firms: Virginia
Over 600 firms: Duke, Michigan, NYU
Over 500 firms: Berkeley, Chicago, Columbia, Penn, Stanford
Over 400 firms: George Washington, Howard, Northwestern, Texas, Yale
Over 300 firms: Cornell, UCLA, Vanderbilt
Over 200 firms: Boston College, Boston Univ., Emory, Fordham, North Carolina, Notre Dame, Southern California, UC Hastings, William & Mary (and Washington & Lee is very close, with 197)
Over 150 firms: UC Davis
Over 100 firms: American, Colorado, Florida, Georgia, Houston, Illinois, Iowa, Loyola/Los Angeles, Minnesota, SMU, Tulane, Wake Forest, Wash U/St. Louis, Wisconsin
72-94 firms: Baylor, Brigham Young, Brooklyn, Cardozo, Case Western, Catholic, George Mason, Indiana, Miami, Ohio State, Rutgers-Camden, Rutgers-Newark, San Diego, Santa Clara, Temple, Villanova, Washington/Seattle
49-66 firms: Chicago-Kent, Cincinnati, Connecticut, Denver, Florida State, Kansas, LSU, Maryland, Oregon, Penn State, Pittsburgh, San Francisco, Seton Hall, South Carolina, South Texas, St. John's, Tennessee. (And on the cusp: Arizona , Loyola-Chicago , Mississippi , Utah , Georgia State , Missouri-Columbia .)
A sampling of some others: New York Law School-36; Alabama-34; Wayne State-29; Hofstra-27; Pepperdine-21; McGeorge-19; SUNY-Buffalo-16; Syracuse-16; Cal Western-10; Hawaii-8; Chapman-4; Cooley-3.
One reasonable interprtation of this data is that there are about 20 "national" law schools, and another ten-or-so borderline national law schools.