The UC Regent Live blog has the best information so far on the breaking news overnight regarding at least one noose found hanging in UCSD's Geisel Library around midnight Pacific Time. The blog reports two people saying that the main student newspaper, The Guardian, received a note saying that more nooses are coming. The blog includes a photograph of the noose and reports that (as of about 2:20 a.m.) the police have no eyewitness accounts of the noose being placed, that there "are no cameras in that area of the library," and that the police have opened a criminal investigation and have dusted the area for fingerprints and have removed the noose "so they can run a DNA analysis." The blog also reports that people will be gathering on Library Walk at 8:00 a.m. today (Pacific Time) in response.
I think it's fair to presume that you're not allowed to hang anything in the library without permission (except, perhaps, posters in designated areas). Thus, regardless of the message that was intended, and regardless of the expressive aspects of hanging the noose, this action is not protected speech. In addition, a commenter on the blog points out that nooses are treated specially (PDF; see page 36) under California law.
Regardless of the intentions of whoever placed it, the noose is likely to increase racial tensions at UCSD, which are already high. The incident is likely to make UCSD's freedom of expression issues even harder to resolve in a fair and constitutional manner. Let's be clear: hanging the noose is, at the very least, the crime of vandalism. It is not protected speech, and whatever the motivation behind it, whoever did it had to have known that it was making the situation worse at UCSD. The police are doing the right thing in investigating this conduct, and I hope the offender or offenders are brought to justice.