University Ethics and Political Campaigning

The University of Illinois recently announced that to comply with the ethics rules of the state, no university employee may engage in political activity while on campus. Check out the University’s statement here.
In response the American Association of University Professors (AAUP) has released the following statement:

THE AAUP REAFFIRMS GRAD EMPLOYEE AND STAFF RIGHTS

According to University of Illinois President Joe White and his Ethics Office, a UI secretary, carpenter, graduate employee, academic professional or faculty member is in violation of the university’s regulations if one of them returns to campus at night to attend a political rally. Wearing a campaign button at the rally would make them doubly unethical.
The US constitution guarantees freedom of assembly and freedom of speech. Does the university have an interest that would justify overriding these rights for employees, something it knows it cannot do for students, who retain their rights as citizens when they walk across the campus? The state has an interest in ensuring that its citizens are not deprived of information