The supreme court in Nepal has annulled a controversial anti-corruption panel set up after the 2005 royal coup.
King Gyanendra has pledged to stamp out corruption
The court said the Royal Commission for Corruption Control was unconstitutional and its rulings should be invalidated.
The court order could lead to the release of former Prime Minister Sher Bahadur Deuba, whom the commission jailed on corruption charges last July.
Critics of the king, who sacked Mr Deuba on seizing power, say the panel acted as prosecutor, judge and jury.
Mr Deuba, one of dozens of people jailed by the commission, said he had been framed and refused to testify.
The BBC's Charles Haviland in Kathmandu says the supreme court ruling is another blow to King Gyanendra after local elections last week drew a turn-out of only 20%.
'Rule of law'
In landmark ruling, the supreme court said the commission had been set up "against the norms and spirit of the constitution".
The five judges were unanimous in ordering that the panel be scrapped with immediate effect.
Shambhu Thapa, president of the Nepal Bar Association, hailed the verdict as "a victory for the rule of law".
"It shows that nobody is... above the constitution," he told the AFP news agency.
King Gyanendra set up the commission immediately after seizing direct power and declaring a three-month state of emergency on 1 February 2005. Leading opposition figures were arrested.
Tackling corruption and crushing a bloody Maoist revolt were key stated aims of his coup.
Critics said the anti-corruption body was given unconstitutional powers to charge, try and punish the king's opponents.