When do professors have to pay for each digital, partial copy of published works they assign students -- and when can they buy once and copy free?
This 350-page decision, Cambridge University Press et. al. v. Mark Becker, sets some guidelines limiting and focusing the size, purpose and economics of academic copying.

Ruling in the case of three textbook publishers who sued Georgia State University's president for letting professors send chapters and excerpts to students, US District Judge Orinda D. Evans in Atlanta posted a"landmark decision on the nature of copyright law in the digital age," in which she "rejected 69 of the 74 claims" by the publishers while setting some ground rules for "fair use" of copyrighted materials online.
That's according to a statement released by the office of GSU's lawyer, Katrina M. Quicker, and associate Richard Miller, of the intellectual-property department at Ballard Spahr LLP, Philadelphia. They collaborated with counsel from McKeon Meunier Carlin & Curfman and King & Spalding, combining "hundreds" of disputes in the test case. 

"It's the first in-depth analysis of how copyright laws" will apply to digital publicaitions in higher education, Quicker said in a statement. 
Rutgers-Camden Law School Prof. Michael Carrier concurred: "The fair use doctrine is amorphous, providing very little guidance," he told me. "Classroom guidelines that explain how much can be copied don't offer much assistance." 

So the judge has stepped in, offering clarity. Evans' ruling "may be the longest copyright decision I've ever seen," added Carrier, author of Innovation for the 21st Century (Oxford University Press), a textbook on intellectual property.