The Construction, Forestry, Mining and Energy Union and union boss Joe McDonald have been fined $48,000 in the Federal Court for engaging in an unlawful strike at the City Square project in July last year.
On July 15 2009, 143 workers went on strike and the site was shut down after attending a meeting with Mr McDonald.
An initial vote by the workers did not support the industrial action.
"Shutting down a $500 million project for 24 hours is an extreme course of action," said Australian Building Construction Commissioner John Lloyd.
"The law reflects community expectations that building projects should proceed without delays caused by unlawful wildcat strikes.
"The courts will penalise those involved in unlawful industrial action. This decision underlines that fact.
In handing down the penalties of $40,000 on the CFMEU and $8,000 on Mr McDonald, Justice Barker took into account the CFMEU and Mr McDonald's past record for similar contraventions.
Justice Barker noted that "...The BCII Act is plainly designed to ensure that industrial disputation will be resolved by means other than unlawful industrial action."
He found that Mr McDonald understood "... the industrial risks ... in taking the action he exhorted."
