Was a restraining order or criminal protective order issued as a result of the incident?
And I am confused about a contradictory pair of sentences ... you wrote that you and your wife are both students at UCSB and "they are not getting involved." Then, you go on to write that "they" are threatening to expel you from the university. Who are "they?" What did they cite as grounds for such an expulsion?
Did this occur at a fraternity house?
It should be noted that the university does reserve the right to exert authority even to some off campus activity.
From Chapter VIII (SW 101.00):
Other Areas of University Jurisdiction
In addition to privately owned residence halls, the University may exercise jurisdiction over student conduct that occurs off University property. In considering whether to exercise off-campus jurisdiction in an individual case, the following may be considered: the seriousness of the alleged misconduct, whether the alleged victim is a member of the campus community, whether a crime has been reported to the criminal authorities, the risk of future harm involved, whether the off-campus conduct is part of a series of actions that occurred both on and off campus, and the ability of the University to gather evidence including the testimony of witnesses. Any request to extend jurisdiction will be reviewed by the Associate Dean for Judicial Affairs, the Dean of Students, and the Vice Chancellor for Student Affairs, in consultation with a committee composed of faculty and students. All these parties must be in agreement before a case can be formally adjudicated.
Campus regulations applying to off-campus behavior are limited to: Section 102.08 (physical abuse, threats of violence, arson-related offenses, and sexual assault), Section 102.09 (sexual harassment), Section 102.10 (stalking), and Section 102.12 (hazing). For a full description, refer to G in this chapter.
These regs can be found here:
http://www.sa.ucsb.edu/Regulations/student_conduct.aspx
You DO have a right to due process within the university rules. So, if they do seek to expel you, you will have the right to challenge it.