Construction, Forestry, Mining and Energy Union officials performed a haka outside court on Monday morning, as they prepared to face a critical day for both Mr Lomax, and for the organisation's bid to force police to return or destroy huge volumes of material seized during an August raid on its Dickson headquarters.

More than 100 CFMEU members rallied around Mr Lomax, an ACT organiser and former rugby league international, as he headed into the ACT Magistrates Court on Monday to have the blackmail charge against him dropped.

The charge stemmed from evidence at the commission, where it was alleged that Mr Lomax blackmailed a Canberra painting company and its principal into signing a union enterprise bargaining agreement in April last year.

The business owner alleged the EBA forced him to pay much higher wages to workers, and that he signed the deal because he believed he would be blocked from working in the ACT and NSW if he refused.

The charge – one of the most high-profile criminal allegations to stem from the commission's hearings – saw Mr Lomax hauled before the ACT Magistrates Court, where he pleaded not guilty in August.

The case was to be vigorously defended, and Mr Lomax's barrister claimed key elements of the offence had not been met by police in their allegations.

In an embarrassing twist earlier this month, it emerged that prosecutors planned to drop the charges against Mr Lomax.

That course was formally taken by the Director of Public Prosecutions on Monday.

CFMEU members who packed out the courtroom applauded as the charge was withdrawn, and chanted "the workers united, will never be defeated" as Mr Lomax emerged from the building.

Outside court, CFMEU national secretary Dave Noonan said Mr Lomax had been charged for simply doing his job.

"He negotiated a pay rise for workers, that's not a crime in any civilised country in the world," he said.

"The only place that's a crime is in tinpot, Third World dictatorships."

He also hinted at further legal action over what he described as an "absolutely disgraceful prosecution". It is understood Mr Lomax's lawyers are considering whether the prosecution was malicious in nature.

"The Australian Federal Police should not be dragged into the middle of the federal government's war against organised labour, workers and trade unions," Mr Noonan said.

Mr Lomax's lawyer, John Agius, asked for costs to be awarded against the DPP, an unopposed application that was granted by Magistrate Robert Cook.

Earlier on Monday, another man facing a criminal allegation of perjury stemming from his evidence to the commission appeared in the ACT Magistrates Court.

During his evidence before the commission, Tuungafasi Manase – a non-financial member of the CFMEU, but not a union employee – denied he had composed a handwritten note allegedly listing bribes to another union official.

He was warned that he was under oath, before his handwriting was compared with that on the note.

Mr Manase's lawyer, Toni Tu'ulakitau, on Monday maintained his client's plea of not guilty to the perjury charge, and the case was set down for hearing in May next year.

Meanwhile, in the neighbouring ACT Supreme Court, the CFMEU also spent much of Monday arguing its case against the Australian Federal Police over the legality of a lengthy raid on its Dickson headquarters in August.

The union is alleging the confiscation of documentation from the headquarters was unlawful, and is seeking to force the AFP to return or destroy all material seized in the search.

Police are believed to have taken thousands of electronic and hard copy files, as well as mobile phones, while frisk-searching union officials and staff, removing posters, and going through the office safe and ceiling cavity.

They stayed at the headquarters for about 13 hours.

Police have already pledged to not use or examine the information after an injunction was put in place by the court last month.

The hearing continues on Tuesday before Acting Chief Justice Richard Refshauge.