A member of the Irish language rap trio Kneecap is due to appear at the Royal Courts of Justice in London to hear an appeal against the decision to throw out terrorism charges brought against him last year.
Supporters of Liam Óg Ó hAnnaidh have gathered outside the court.
The UK government is appealing the September 2025 decision to dismiss the case against Ó hAnnaidh, which was thrown out on technical grounds relating to how the charge against him was brought.
He was charged last May after allegedly displaying a flag in support of proscribed organisation Hezbollah at a gig at the O2 Forum in Kentish Town, London, in November 2024.
The 28-year-old, who performs under the stage name Mo Chara, had denied the charge and had described it as political.
Supporters arrived just before 09:00 GMT carrying Irish tricolours and Palestinian flags and various signs.
Ó hAnnaidh's defence previously argued that the charge was not brought within the six-month time limit since the alleged offence took place.
In September, Chief Magistrate Paul Goldspring told Woolwich Crown Court that the charge against Ó hAnnaidh was "unlawful" and "null".
In his judgement, the chief magistrate outlined that permission was not given to the Director of Public Prosecutions (DPP) to consent to the prosecution until 22 May, a day after Ó hAnnaidh was charged.
If 22 May was considered to be the date of the charge, that was six months and a day after the London gig where the offence allegedly happened.
The decision did not relate to any of the allegations Ó hAnnaidh had been facing.
Court papers state Wednesday's hearing will hear the case of the DPP v Liam Óg Ó hAnnaidh.
The DPP argues that it was sufficient that the charge was brought before Ó hAnnaidh made his first appearance at court on 18 June 2025 to answer the written charge.
The Crown Prosecution Service (CPS) announced in October 2025 that it would appeal the decision "as we believe there is an important point of law which needs to be clarified".
In a statement issued on social media at the time, Kneecap said the appeal would be "a massive waste of taxpayers money, of police time, of court time".
The group added: "News of a CPS appeal against the ruling of their own judge is unsurprising.
"It is unsurprising, because the whole process has not been driven by the police or courts, it has been driven by politicians backed up by the British media."
They said this is "political policing".
"There is no important point of law. The CPS have submitted nothing new in their appeal. What there is though is a state wide witch-hunt against Palestinian solidarity."
In a social media post earlier this month, Kneecap said the appeal would be heard in the Royal Courts of Justice on Wednesday 14 January.
"It is the view of our legal team that there is not an iota of logic for this [appeal], it is without any sound legal basis," Kneecap added.
Kneecap are an Irish-speaking rap trio who have courted controversy with their provocative lyrics and merchandise.
The group was formed in 2017 by three musicians who go by the stage names of Mo Chara, Móglaí Bap and DJ Próvaí.
Their rise to fame inspired a semi-fictionalised film starring Oscar-nominated actor Michael Fassbender.
The film won a British Academy of Film Award (Bafta) in February 2025.
In April, the group faced criticism after displaying messages about the war in Gaza during their set at US music festival Coachella.
In November 2024, the group won its case against the UK government over a decision Kemi Badenoch took when she was a minister to withdraw an arts grant.