The rapper, who performs under the stage name Mo Chara, was charged in May 2025 with the alleged display of a flag in support of the proscribed terrorist group Hezbollah at a gig in London on 21 November 2024.
But the case against the Belfast-born Kneecap rapper was dismissed last September on technical grounds.
At the time, chief magistrate Paul Goldspring told Woolwich Crown Court that the charge was "unlawful" and he had no jurisdiction to try the case - but prosecutors appealed against the decision.
The High Court ruling was handed down remotely on Wednesday afternoon.
Lord Justice Edis, sitting with Mr Justice Linden, said that "the judge was right to hold that he had no jurisdiction to try any summary-only offence alleged to have been committed on that date".
In the 13-page decision, Lord Justice Edis said their decision "turned on a very narrow and technical legal issue and has nothing to do with whether the respondent committed the offence set out in the charge".
In a statement released through his lawyers, O hAnnaidh said: "This entire process was never about me, never about any threat to the public and never about 'terrorism', a word used by the British government to discredit people you oppress both in Ireland and across the world.
"It was always about Palestine and about what happens if you dare to speak up. About what happens if you can reach large groups of people and expose their hypocrisy."
Speaking at a press conference in Belfast shortly after the ruling, O hAnnaidh added: "This is bigger than us - whatever kind of stress that we felt, it's minimal compared to the stress put on the families in Gaza."
He said the band has "lost gigs" and been "restricted" as a result of the court proceedings, but will continue to use their platform to talk about Palestine as they no longer fear "repercussions".
Following the decision, a CPS spokesperson said: "The High Court has clarified how the law applies to the issuing of written charges in summary offences where attorney general permission was required for the director of public prosecutions to consent to a prosecution.
"We accept the judgment and will update our processes accordingly."
After O hAnnaidh was charged, he first appeared in court in June.
At a second hearing in August, the rapper's lawyers argued prosecutors should have sought the permission of the attorney general, the chief legal adviser to the Crown, to charge him with a terror offence before informing him of the decision on 21 May last year.
This permission was instead given the following day, which meant it fell outside the six-month timeframe in which criminal charges against a defendant can be brought for this type of offence, the court was told.
Anthony Russell, 43, is charged with murdering 52-year-old Huntley at HMP Frankland, near Durham.
He appeared before Newton Aycliffe Magistrates' Court on Wednesday via videolink.
Wearing a grey sweatshirt while sitting at a table, Russell spoke only to confirm his name and that he understood the proceedings.
He will appear at Newcastle Crown Court on Thursday.
A spokesman for Durham Constabulary previously said that "a man has been charged with murder following an incident at HMP Frankland in Durham".
The spokesperson said "emergency services were called to reports of an assault in the workshop" on the morning of 26 February.
The 52-year-old was taken to hospital with serious injuries, but died on 7 March.
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Huntley was convicted of the murders of 10-year-olds Holly Wells and Jessica Chapman in Soham, Cambridgeshire, in 2002.
He killed them after they left a family barbecue to buy sweets, then dumped their bodies in a ditch.
He was convicted of the murder of both girls in December 2003 and sentenced to two terms of life imprisonment.
Officers were called to Thorpe St Andrew School, Laundry Lane, Thorpe St Andrew, at 10.24am on Wednesday following reports a girl had been stabbed.
A 16-year-old boy has been arrested on suspicion of causing grievous bodily harm with intent, Norfolk Police said.
The boy has been taken to Wymondham police investigation centre for questioning, the force added.
The victim has been taken to hospital with minor injuries.
Emergency services including fire and ambulance crews were at the scene.
Armed police officers were also at the school, reported the Eastern Daily Press.
The school went "into lockdown" and children remained in their "classroom with their teacher".
Owen Jenkins, the chief executive of Broad Horizons Education Trust, which runs the school, said: "We have clear procedures in place and our staff acted swiftly, with the whole school going into lockdown with children staying in their classroom with their teacher.
"One of our students was injured and is now being treated in hospital for minor injuries.
"This has obviously been a distressing experience for our whole community and our focus now is on making sure all students feel supported as we begin to understand what happened."
Norwich North MP Alice Macdonald wrote on social media: "Reports from Thorpe St Andrew School are incredibly serious and deeply alarming.
"Immediately, we need to give the police time to ensure that everyone at the school is safe.
"My thoughts are with all of them and their families, especially the victim who has been taken to hospital."
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The school, which was rated "Good" in its 2025 Ofsted inspection, is an 11 to 18 mixed secondary school which also includes a sixth form.
The incident is not believed to be linked to a hate crime reported at the same school last week, police added.
It followed reports of allegations of antisemitic chanting during a football match involving a Jewish school.
The driver has been arrested in Washington DC and no injuries have been reported, a police spokesman said.
Officers were called at about 6.37am local time "to the vicinity of the White House... after a van drove through the barricade at Connecticut Avenue and H Street, Northwest", he added.
The Secret Service said the man crashed into the temporary security barrier just before 6.30am (10.30am in the UK).
He was immediately arrested by officers from the Secret Service's uniformed division, the agency said, adding that he was being interviewed and that criminal charges were pending.
A police bomb squad was called to the scene, checked the vehicle and determined it to be safe.
The team's participation has been in doubt after US and Israeli forces struck Iran, with Tehran retaliating with attacks on American assets and allies across the Middle East.
Follow the latest on the Iran war
FIFA boss Gianni Infantino said earlier that he met US President Donald Trump on Tuesday night "to discuss the status of preparations" for the tournament, and received assurances Iran would be welcome to compete in the World Cup, co-hosted by the US, Mexico and Canada.
However, Iran's sports minister Ahmad Donyamali told state television that "considering that this corrupt regime has assassinated our leader" - Ayatollah Ali Khamenei - "under no circumstances can we participate in the World Cup".
According to state news outlet WANA, the head of Iran's football federation Mehdi Taj also said: "Which rational person would send the national team into such a situation?"
Iran's men's national team are scheduled to play in the US against New Zealand in June, before facing Belgium and Egypt.
Last week, Mr Trump, who received FIFA's inaugural peace prize last year, said that "I really don't care" if Iran takes part in the tournament.
In a post on Instagram on Wednesday, Mr Infantino said that during discussions last night, "President Trump reiterated that the Iranian team is, of course, welcome to compete in the tournament in the United States".
"We all need an event like the FIFA World Cup to bring people together now more than ever, and I sincerely thank the President of the United States for his support, as it shows once again that Football Unites the World," Mr Infantino added.
It comes after six members of the Iranian women's football team - five players and one member of staff - were granted humanitarian visas to remain in Australia over fears they could be in danger after they did not sing Iran's national anthem before a game. They were in Australia for the Asian Cup.
One player on the team has since decided to return to Iran.
A travel ban imposed by Mr Trump means Iranian fans will not be able to travel to America this summer, but teams are due to be given exemptions to participate.
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FIFA's World Cup chief operating officer said earlier this week that the tournament is "too big" to be postponed because of global turmoil caused by the Iran war.
Heimo Schirgi said: "The World Cup will go on obviously, right? The World Cup is too big, and we hope that everyone can participate that has qualified."