Lawyers in Nepal have said they will boycott the powerful anti-corruption body set up by King Gyanendra after he assumed direct power in February.
Bar president Sambhu Thapa (left) addresses lawyers in Kathmandu
The Nepal Bar Association said the Royal Commission for Corruption Control was unconstitutional.
The commission has the power to try and sentence former politicians and government figures accused of graft.
The king assumed direct power because, he said, politicians were corrupt and failed to deal with Maoist insurgents.
The lawyers' move comes after sacked prime minister, Sher Bahadur Deuba, who is being investigated by the commission, said he would stay in detention rather than pay bail to it.
Mr Deuba has been behind bars for five weeks accused of embezzlement.
The Supreme Court Bar Association and the Nepal Bar Association have both said their members must now boycott the commission and not appear before it to defend an accused person.
Sambhu Thapa, president of the Nepal Bar Association, said: "The commission was illegally constituted. We can't take part in something that is not within the constitution."
The commission's critics have accused it of flouting the law by combining the role of prosecutor and judge and of lacking legal expertise.
It comprises ex-government administrators, a general and an intelligence officer.
The government has been accused of acting unlawfully in other areas, including by forbidding radio stations to report news, by re-arresting people freed on Supreme Court orders and by changing the rules for appointments to the National Human Rights Commission.
Separately on Wednesday, the Kathmandu office of the International Committee of the Red Cross said it had put on hold visits to detainees at army barracks throughout Nepal for the past month.
The Red Cross would not say why but other sources said the army had failed to comply with agreed visiting practices.
The Red Cross said it hoped to resolve the problem soon.
The army says its barracks host some detainees, mostly Maoists, for security reasons.