Rebel lawmaker Leung Kwok-hung could be thrown out of the Legislative Council if he fails in his appeal against a two-month jail term.
Leung was one of five people given jail terms yesterday after being found guilty of criminal damage and acting in a disorderly manner in a public place.
"Long Hair" Leung was granted bail of HK$1,000 pending an appeal. He was also fined HK$4,150 for damaging a glass door and plants at the museum.
A defiant Leung said outside Kowloon City Magistrates' Courts he has no regrets even if he does end up in jail.
"You can lock up my body, but you can't lock up my soul," he said. "I have no regrets."
Leung was sentenced to two months, while the other activists - newspaper columnist Wong Yeung-tat, mechanic Yung Wai-tong, and students Tang Kin- wa and Chan Sin-ying - were each jailed for three weeks.
The court was told that about 100 protesters, led by Leung, barged into a consultation session on the government's proposals for changing the way by-elections for the Legislative Council are conducted.
They gatecrashed the session at the Hong Kong Science Museum in Tsim Sha Tsui last September, sparking scuffles with security guards and those taking part.
The forum speaker, then- constitutional affairs secretary Stephen Lam Sui-lung, and others were forced to flee backstage.
If Leung loses his appeal and serves time behind bars, his famous locks will be shorn, likely giving him the new nickname "Short Hair."
Magistrate Peter Law Tak-chuen said their protest was chaotic and out of control, posing a danger to hundreds of citizens taking part in the forum.
Law said that if people had fallen in the incident, it could easily have triggered a stampede resulting in casualties.
Such rallies had already caused a great nuisance to the public, Law said.
According to Article 79 (6) of the Basic Law, a lawmaker convicted and sentenced to imprisonment for one month or more for a criminal offence committed in or outside Hong Kong can be expelled from Legco by a motion passed by two-thirds of the legislators present.
Outside court, Leung said it was unfair of the court to impose such a heavy sentence on him as he simply staged the rally to voice opposition to the government's by-election proposals.
Legco president Jasper Tsang Yok- sing said he will consult the legislature's lawyers on how to activate the expulsion mechanism stipulated in the Basic Law.
Tsang said he will start the process if any lawmaker raises a motion in Legco seeking to expel Leung.
Lawmaker Chim Pui-chung, who represents the financial services functional constituency, said he will support a motion to expel Leung. Chim was expelled from the legislature when he was jailed for conspiracy to forge share transfer documents in 1998.
However, Democratic Alliance for the Betterment and Progress of Hong Kong lawmaker Ip Kwok-him said: "We will discuss whether to support a motion to expel Leung as there are just months left before the Legislative Council elections in September."
Democratic Party lawmaker Wong Sing-chi said he does not support such a motion as it will take several months to handle the matter and it is not worth spending a huge sum on a by-election.
The forum was one of two the government held to consult the public on a by-election proposal, which it introduced after Leung and other pan- democrat lawmakers resigned in January 2010 to force what they called a de facto referendum on universal suffrage.