The society’s writ alleges a paper-based assessment of the Gunns’ project, ordered by Environment Minister Malcolm Turnbull after the company withdrew from a far broader integrated assessment, is illegal.
It claims Mr Turnbull has breached his own legislation by effectively allowing Gunns to "process shop" and move to a less rigorous assessment than that Resource Planning and Development Commission process.
A three-day hearing is scheduled to start on Wednesday. The CFMEU’s application seeks an order today that it be allowed to join proceedings.
It includes an affidavit from CFMEU national secretary John Sutton arguing the union has a direct interest in the pulp mill project proceeding.
"If the pulp mill at Bell Bay proceeds there would be employment opportunities for existing CFMEU members and a likelihood that the CFMEU would gain further members," Mr Sutton says in it.
"Members would be engaged in the construction of the mill and in the operation and maintenance of the mill.
"If the mill does not proceed, the security of resource for the entire pulp and paper and forestry industries will be less secure and the employment of existing workers who are members of the CFMEU would be less secure."
Wilderness Society spokeswoman Virginia Young said the union’s legal manoeuvre demonstrated its "very close relationship" with the Coalition.
"We’re a bit puzzled by it, given that I wouldn’t have thought either the commonwealth or Gunns would need financial help in the case," Ms Young said.
CFMEU (forestry division) national secretary Michael O’Connor would not comment on the case but said the union firmly believed the project should proceed.