Officials at London City Airport, citing "unresolved convictions in the USA," detained the rapper after he arrived to perform at a concert in the capital’s Royal Albert Hall on Friday.
"A High Court judge ordered his release this evening. He has been allowed entry into the UK having been detained all day at London City Airport," said a spokeswoman for concert organizers RockCorps.
She said his appearance at the event would depend on the outcome of a judicial review due to be held on Friday.
"We’re very hopeful he’ll be playing the show," she added.
RockCorps is a volunteer project which rewards youngsters with free concert tickets in return for doing four hours of charity work.
Immigration officials tried to put Rhymes on a flight to Amsterdam but his lawyer obtained an injunction and applied for a judicial review of the decision not to grant him admission, said cell phone operator Orange, which is promoting the concert.
This year Rhymes was sentenced to three years’ probation for beating a fan who spat on his car in August 2006 and assaulting his driver that December.
"He has the necessary work permit and has been in the country twice already this year, so we’re a little puzzled that a question mark is now being placed over his ability to enter the country to perform to volunteers," said Stephen Greene, co-founder of RockCorps.
"We’re shocked at this sequence of events and this treatment of Busta."
The London show, which will feature British bands The Automatic, Feeder and U.S. soul singer John Legend, is being held for 5,000 fans who clocked up a total of 20,000 hours of voluntary work.
Britain’s Home Office said previous criminal convictions and a person’s character and conduct were assessed before an individual was allowed into the country. Reuters