A Hong Kong man has been sentenced to 14 months in jail after pleading guilty to sedition for wearing a T-shirt with a protest slogan on it.

The jail term is the first handed down by the city’s court under a new local national security law that was passed in March.

The law, also called Article 23, expands on the national security law that was imposed by Beijing in 2020.

Critics feared the law could further erode civil liberties in the city, while Beijing and Hong Kong defended it, saying it was necessary for stability.

Chu Kai-pong, 27, was arrested at a subway station in June wearing a T-shirt sporting the phrase “Liberate Hong Kong, revolution of our times”. He was also wearing a mask that read “FDNOL” – initials for another slogan, “Five demands, not one less”.

Both slogans were frequently heard in large-scale protests in Hong Kong during the months-long anti-government demonstrations in 2019. Local media reported he was also carrying a box containing his excrement to use against people opposing his views.

Chu was arrested on 12 June, the anniversary of a key date of the 2019 protests when particularly large crowds took to the city’s streets.

The court heard Chu told police he wore the T-shirt to remind people of the protests, according to Reuters. He was previously jailed for three months in a separate incident for wearing a T-shirt with the same slogan, as well as possession of other offensive items.

Chu has been remanded in custody since 14 June. On Monday, he pleaded guilty to one count of doing an act with a seditious intention”.

In a statement released on Thursday, chief magistrate Victor So, who was handpicked by the government to hear national security cases, said Chu intended to “reignite the ideas behind” the 2019 protests.

He said Chu “showed no remorse” after his previous conviction, and that the sentence reflected the “seriousness” of the sedition charge.

The conviction and sentencing have been criticised by human rights groups. Amnesty International’s China director Sarah Brooks described it as “a blatant attack on the right to freedom of expression”, and called for the repealing of Article 23 in a statement.

The sentencing comes after a landmark ruling of another case last month, when two journalists who led the pro-democracy newspaper Stand News were found guilty of sedition. That marked the first sedition case against the city’s journalists since Hong Kong’s handover from Britain to China in 1997.