A government policy to ban inmates with a history of absconding from being transferred to open prisons has been declared unlawful by senior judges.
Justice Secretary Chris Grayling introduced the policy last year after high-profile cases of violent prisoners absconding from open prisons.
But two judges at London's High Court said such bans were inconsistent with Mr Grayling's own parole directions.
A Ministry of Justice spokesman said it would appeal against the ruling.
Prisoners can be moved to open prisons - also known as category D prisons - if the parole board finds they are not a danger to the public or other inmates, or they are unlikely to abscond.
Prisoners are often moved to open prisons towards the end of their sentence.
Inmates can then be given release on temporary licence (ROTL), allowing them to leave the jail for a few hours or even overnight.
Last year, Mr Grayling said the government was "tearing up" the current system and introducing restrictions on known absconders, following a number of high-profile escapes.
However, Lord Justice Bean, sitting with Mr Justice Mitting, ruled the policy of excluding such transfers - except in exceptional circumstances - was inconsistent with government directions to the parole board.
The directions state that "a phased release" from a closed to an open prison is necessary for most inmates "in order to test the prisoner's readiness for release into the community".
A Ministry of Justice spokesman said it would appeal the decision, saying the "fundamental principles of the policy are not unlawful".
"The court found there was inconsistency with the implementation. Our position remains that temporary release can be an important part of rehabilitating offenders but not at the cost of public protection," the spokesman said.
The Prisoners' Advice Service, which offers free legal advice and support to adult prisoners, said the absconder policy had been a "knee-jerk reaction".
"The secretary of state's contention that he is entitled to ignore and contradict his own policy guidance demonstrates either his ignorance or flagrant disregard for basic legal principles of consistency and transparency in public decision making.
"The so called 'absconder policy' was introduced as a knee-jerk reaction to negative press reports without adequate consideration for either existing policies, or its impact on the prisoners whose progression to open conditions was abruptly prevented," the charity said in a statement.