Ted Seto (Loyola/LA) has some interesting observations here. (See also the first comment there.) Professor Seto is surely right that the biggest problem for US News, if schools refused to report data, is that the magazine would have no access to the per capita expenditures data, which is often the tail that wags the ranking dog (Yale is #1 in US News only because of per capita expenditures, which favors small schools like Yale against very large schools like Harvard). We know, however, from the college rankings that when schools don't cooperate, US News simply supplies "guesstimates" for the missing data. In the case of the law school rankings, they will have multiple years worth of expenditures data on which to make a projection, though presumably it will be a conservative, rather than generous, estimated, meaning any school that doesn't cooperate will almost certainly fall in US News. And, as we have discussed before, explaining a fall is always much harder than explaining a rise (which requires no explanation!), especially given the bad habit of journalists of reporting the overall US News rank as though it meant something.
The bottom line, then, is that most law schools will not boycott, unless they are confident that most other schools are boycotting. And that is only likely to happen if the schools that can most easily withstand being abused by US News--namely, Harvard and Yale--step forward and declare that they are done supplying data to the magazine.
So Deans Kagan and Koh, it's up to you!
Meanwhile, we will await Mr. Morse's response to our "open letter."