More than a hundred angry unionists have marched on parliament house as the embattled CFMEU's forced administration is challenged in Australia's highest court.
The Construction, Forestry and Maritime Employees Union (CFMEU) is dealing with allegations of links to organised crime as administrator Mark Irving works to clean up the organisation.
Laws forcing a takeover of all branches of the militant union's construction arm have been heavily protested by some blue-collar unions, including the Electrical Trades Union (ETU).
The Fair Work Ombudsman has opened more than 40 investigations into the commercial building and construction industry and hundreds of CFMEU officials were sacked after the takeover.
The ETU led a rally outside parliament house in Canberra on Tuesday as the two-day High Court hearing began.
Chants of "union power", "the workers united will never be defeated", "one law for all" and "what do we do when we're under attack? Stand up fight back" rung out during the hour-long protest.
The laws threatened the rights of all union members and set a dangerous legal precedent, ETU national secretary Michael Wright said.
"This s*** is not that complicated, if there are allegations, they go to court, they don't go to parliament, they don't do trial by media," he told the rally.
"You have your day in the court and right or wrong, you live with the result."
Win or lose in the High Court, the future of the union remained in the hands of its members, Mr Wright said.
"When I look out at all the faces that I see here today, I feel nothing but pride and hope, because I see people who are here to demand respect," he said.
Taking over the entire union amounted to collective punishment, former CFMEU Victorian branch secretary Ralph Edwards told the rally.
"We are being treated no better, in one sense, than people in Gaza and people in south Lebanon," he said.
Other unions could be next, he warned.
"They are planning for everybody. If you don't fight, you lose."
Sacked CFMEU officials Michael Ravbar and William Lowth brought the case before the High Court, arguing being put into administration infringed the implied freedom of political communication.
The legality of the powers granted to put the constructive and general division into administration is also being challenged.
The Commonwealth rejects these arguments.
Pending the outcome of the High Court challenge, the legislation allows the CFMEU to remain in administration for up to five years and officials that frustrate or obstruct the process face hefty penalties.
