"The judicial panel decided that the court lacks the jurisdiction to look into the case," said the lawyer Khalid al-Mutairi after the closed-door hearing in Riyadh on Wednesday.
The case will go to the court of summary justice, which is presided over by only one judge and specialises in crimes with no legally defined punishment.
Referring the case to a "court with jurisdiction to look into it" was the wish of the defence team since the beginning of the trial, said al-Mutairi.
Ali al-Damaini, Abd Allah al-Hamid and Matruk al-Falih were arrested on 16 March. They are also accused of "using Western terminology" in demanding political reforms and of questioning the role of King Fahd as head of the judiciary.
Al-Damaini's wife said a handful of relatives were allowed to attend, but that they refused "protesting against the presence of plainclothes policemen inside the courtroom".
She said the police were brought in "to sit in as attendants and fake the openness of the hearing".
Reformists question King Fahd's
role as head of Saudi judiciary
Moments before the hearing resumed, seven supporters were arrested at the courthouse, including two of al-Hamid's brothers, witnesses and an AFP journalist said.
Shahid Khan, a journalist for the English-language Saudi Gazette, and Abd Allah al-Abdali, a colleague from the daily Al-Madina, were also detained, they said.
Security forces had cordoned off all entries to the courthouse and dozens of people were pushed away from the main courtyard under the threat of force.
"It is disappointing to see people wanting to attend the hearing get arrested instead," said a Western diplomat, who was also barred from attending, after witnessing the arrests.
According to the diplomat, putting people on trial calls into question the government's commitment to reform.
"If they (government) then close the trial to the public, arrest lawyers and (detain) people who simply want to attend ... that undermines the credibility of the government's commitment to reform," he said.
The head of the officially unrecognised Saudi Human Rights First Association said the police had over-reacted.
"If they (government) then close the trial to the public, arrest lawyers and (detain) people who simply want to attend , ... that undermines the credibility of the government's commitment to reform"
a Western diplomat
"Most of those who wanted to attend are peaceful professionals and do not wish to cause disturbance," said Ali al-Mugaitib.
The trio, who went on trial on 9 August, refused to testify during the last hearing on 4 October in protest at the closed proceedings.
In November, authorities arrested the defence team spokesman, Abd al-Rahman al-Lahim, who had repeatedly and publicly criticised judicial practices during the trial.
The defendants were among a dozen activists arrested at the same time. Half were released within a couple of days after pledging to refrain from publicly lobbying for reform. Three more were freed at the end of March.