The university started a legal challenge in February following a £585,000 penalty imposed by the Office for Students (OfS) after Prof Stock was hounded from her post by transgender activists.

Mrs Justice Lieven, the High Court judge presiding over the case, upheld the university’s complaint in a judgment handed down on Wednesday.

It means the record £585,000 fine has now been overturned. The decision is expected to reignite a debate over free speech on campus, days after the Government confirmed it would push ahead with measures to protect academic freedom at universities in England.

The higher education watchdog spent three-and-a-half years investigating the University of Sussex’s handling of the treatment of Prof Stock. The former philosophy professor was forced out from her job at the University of Sussex in 2021 in what she claims was a “witch hunt” over her gender-critical beliefs.

Prof Stock, an expert in analytic philosophy, resigned from her position after she faced death threats. At the time, students erected posters around campus and called on the university to dismiss her.

Her case prompted widespread calls for tougher protections for academics and to ensure universities remain places of open debate.

In a report published last March, the OfS sided with Prof Stock and found that the university “failed to uphold” freedom of speech and academic freedom, and should be hit with a record fine.

The watchdog also found that “a chilling effect arose” from the University of Sussex’s transgender policy that left staff and students feeling “self-censored” and unable to express “lawful views”.

The University of Sussex contested the ruling and argued in a judicial review that the £585,000 fine should be quashed as “unlawful”, “unreasonable” and “procedurally unfair”.

In her judgment on Wednesday, Mrs Justice Lieven said the watchdog’s findings were “vitiated by bias because the OfS approached the decision with a closed mind and had therefore unlawfully predetermined the decision”.

She also found that the regulator acted beyond its powers by treating the university’s trans and non-binary equality policy statement as a “governing document”. 

Mrs Justice Lieven also said it was wrong for the OfS to interpret a violation of lawful speech as a fundamental breach of the university’s regulatory requirements. 

Prof Sasha Roseneil, the Vice-Chancellor of the University of Sussex, said Wednesday’s judgment would cast doubt on the effectiveness of the OfS altogether.

“Today is a good day for the University of Sussex, and a good day for everyone who cares about the proper and effective governance and regulation of universities,” she said.

“I will today seek a meeting with the Secretary of State for Education to discuss this excoriating judgment and its implications for the higher education sector.

“We need a regulator that can be trusted, that properly understands freedom of speech, academic freedom, lawful commitments to inclusion, and the scope of its own powers. We need a regulator that works with the sector, not against it – in the interests of the students of today and of the future.”

The Free Speech Union (FSU), which acted as a third party in the court case to defend the OfS, said the ruling had “effectively hung Kathleen Stock out to dry and given a green light to trans activists to hound off campus anyone they disagree with”. 

Lord Young of Acton, General Secretary of the FSU, said “This is a terrible judgment which effectively renders the Higher Education (Freedom of Speech) Act toothless. It sends a message to universities that they only need to pay lip service to the new free speech duties in the Act and not actually do anything concrete to uphold academic freedom and free speech on campus. 

“The judge has effectively hung Kathleen Stock out to dry and given a green light to trans activists to hound off campus anyone they disagree with. We very much hope the Office for Students appeals and if it does we hope to intervene.”