The High Court on Friday rejected a bid by an inmate jailed for inciting secession to challenge the authorities' decision denying him early release under the city's homegrown national security law.

Ma Chun-man, also known as “Captain America 2.0” for dressing up as the comic book character at anti-government protests in 2019, was jailed for five years for promoting “Hong Kong independence”.

After serving two-thirds of his sentence in March, Ma was denied an early release normally granted for good behaviour in prison, in line with the provisions of Article 23 national security legislation.

The Commissioner of Correctional Services made the decision two days after the new security law took effect, saying he was "not satisfied that an early release of the prisoner will not be contrary to the interests of national security".

Ma filed a judicial review, arguing it was unfair and that the commissioner should have taken into account his “legitimate expectation” for early release.

In a written judgement handed down on Friday, judge Alex Lee ruled that the commissioner's decision was a "holistic, predictive and evaluative exercise based on a consideration of all the relevant factors".

Ma also failed to explain how his "legitimate expectation" of an early release would affect the national security assessment, the judge added.

"I am unable to see how the fact that a prisoner based on the past practice of the CSD [Correctional Services Department] has a 'legitimate expectation' for early release may either increase or reduce the national security risk that might arise from his or her early release," Lee wrote.

The ruling means Ma will need to serve his full term until November next year.