The lawsuit by the Howard Jarvis Taxpayers Association, filed in Monterey County Superior Court, said the email was sent from a university Internet address to more than 360 CSU-issued email addresses.
It urged recipients to support Proposition 30 and push others to vote for it, while warning of dire consequences if it fails. It also noted that students would receive a $498 tuition reimbursement if the initiative passes.
"The fate of Proposition 30 on the upcoming November ballot will directly affect our university (and our jobs)," said the email from Ernest Stromberg, a professor in the Division of Humanities and Communication.
He goes on to say that if voters reject the initiative, the CSU system will have to cut $250 million from its budget.
"This will include the very real possibility that faculty and staff will face threats of layoffs, furloughs, and other draconian cuts," Stromberg said in the email.
Because the email was sent using university-issued equipment, it violates California campaign law that prohibits the use of public resources for mass political mailings, the lawsuit states.
In a written statement released by CSU, university attorney Christine Helwick called the unauthorized email "inappropriate and unfortunate." She said it was sent by the professor, not on behalf of the university.
"We have previously reminded faculty and staff that it is not permissible to use state resources, including classroom time, for any political advocacy," she said. "This email clearly crossed that line and the campus is taking appropriate personnel action."
Telephone messages left for the professor and the Division of Humanities and Communication were not immediately returned.
Proposed by Gov. Jerry Brown, Proposition 30 would raise the state sales tax by a quarter cent and raise income taxes on those making more than $250,000 a year to help balance the state budget. If it fails, the budget calls for $6 billion in automatic spending cuts, mostly to K-12 schools.