Australia's oldest university has given its students the green light to protest against controversial speakers on campus despite government concerns that freedom of speech is under threat from activist students.

The University of Sydney hired external investigators to examine a protest targeting an event last year featuring journalist and author Bettina Arndt, which sparked a Morrison government inquiry into free speech at Australian universities.

The University of Sydney said it was satisfied the protest did not contravene freedom of speech. Credit:Louise Kennerley

The nine-month investigation resulted in disciplinary action against one student, protest organiser Madeline Ward, but otherwise cleared students of misconduct or breaching the university's guidelines on freedom of expression.

Police were called to the campus after "scuffles" broke out between protesting students and members of the Sydney University Liberal Club, which had invited Ms Arndt to speak as part of her "Fake Rape Crisis Tour" in September.