Australia would be no better than a "tinpot dictatorship" and turn its back on a century of industrial progress if John Lomax were convicted of blackmail, the construction union says.
The Construction, Forestry, Mining and Energy Union said it feared the case could become a precedent that would open the door for future criminal prosecutions targeting union officials during industrial negotiations.
Lomax – a CFMEU organiser who played 65 games for the Canberra Raiders from 1993 to 1996 – was last week charged with one count of blackmail.
He is scheduled to appear before the ACT Magistrates Court next week.
Police will allege that Lomax forced a Canberra painter to sign a union enterprise bargaining agreement in April last year.
The owner believed he would be blocked from working in the ACT and NSW if he did not sign.
It is understood police will allege the owner suffered a financial loss as a result because he had to pay his workers $26 an hour when he could have paid as low as $17.
CFMEU national construction secretary Dave Noonan said Lomax would plead not guilty on the charge and pledged to throw the union's full weight behind his defence.
Lomax is the third person to be arrested by police attached to the commission, and the second person associated with the ACT CFMEU branch after former organiser Halafihi "Fihi" Kivalu was charged with two counts of blackmail.
He has pleaded not guilty.
The Lomax prosecution has left Mr Noonan questioning why the police became involved in an industrial matter.
Mr Noonan said employers, workers and unions all had rights that are set out in the Fair Work Act.
The act provided options for parties who believed the other side had not acted in good faith.
He said to revert to criminal law in such a matter was unprecedented in Australia.
"There's been a legal framework for this for more than 100 years and there are very clearly set-out rights and responsibilities for parties negotiating agreements.
"But what we see here is entirely different, we're seeing an attempt by Tony Abbott's royal commission to use criminal law in what are legitimate employment matters.
"The union is extremely concerned about this precedent, asking for a pay rise shouldn't be a crime but it appears in Tony Abbott's Australia it is going to be treated as one."
The police would not have acted if the situation were reversed, and an employer had failed to pay full conditions and entitlements, or had pressured staff not to sign an EBA, Mr Noonan said.
"The police have got an important role in enforcing criminal law and we respect that, [but] asking for a pay rise and the union negotiating better wages and conditions for its members is not a criminal matter, or at least it's not in democratic modern countries.
"If this becomes the norm, any union, any unionist, or any worker using normal negotiating tactics to try and get a pay rise could also be targeted."
He said the CFMEU had expressed those fears to the Australian Council of Trade Unions.
"If Mr Lomax is convicted – and I'm not suggesting he is because this case is going to be fought and fought hard – for merely asking that a contractor sign an EBA then Australia would be putting itself in the position of a tinpot dictatorship.
"It would be rejecting 100 years of Australian industrial law and progress and it would be a gross breach of the conventions of the International Labour Organisation around collective bargaining and freedom of association which Australia has ratified."
Despite the concerns, he pledged the attack would not stop the construction union representing the best interests of its members.
"In terms of negotiating wages and conditions for our members, the CFMEU have a proud history of that, we have some of the best agreements for workers in the country – construction is a tough industry and we're not going to back off from doing legitimate things a union needs to do to ensure its members get decent wages, decent working conditions, and good safety on site."