Subpoenas dismissed as 'overbroad and burdensome'.
The Attorney General of Oregon State has blocked attempts by the Recording Industry Association of America (RIAA) to spy on university students.
The RIAA had issued subpoenas against 17 students at the University of Oregon, claiming that they had downloaded music from the internet and violated copyright.
Documents filed in the US District Court in Eugene by the Attorney General described the subpoenas as "overbroad and burdensome".
"We do not think the university can be compelled to produce investigative work for the recording industry," Deputy State Attorney General Pete Shepherd told Associated Press.
Court documents issued by the Attorney General's office said: "The university's efforts thus far have been met by accusations that it is obstructing the process and even conspiring with law breakers. Those accusations are not warranted.
"The record in this case suggests that the larger issue may not be whether students are sharing copyrighted music, but whether investigative and litigation strategies are appropriate."
The RIAA has implemented a strategy of tracking illegal downloads to university campus networks and asking for offenders to be identified.
The tenth wave of this initiative was started on 15 November when the RIAA sent 417 pre-litigation settlement letters to 16 universities, including Columbia, Princeton and Yale.
The RIAA encourages offenders to resolve the copyright infringement claims on its dedicated P2P Lawsuits website "at a discounted rate before a formal lawsuit is filed".
Oregon's move is a blow for the RIAA, which has also been hit by rumours this week that EMI wants to scale back its contribution to the organisation.
An unnamed source at EMI told Reuters that the music label is looking "substantially" to reduce its funding of trade groups, including the RIAA.