A writ against the governing body was lodged on Monday evening, Western Australia's rugby body said.
A writ against the governing body was lodged on Monday evening, Western Australia's rugby body said, notifying the ARU of the intention to apply for an injunction against any plan to revoke the Perth-based team's licence.
It followed meetings between the two sides in the wake of the ARU announcing that either the Force or Melbourne Rebels would be culled from the revamped 2018 southern hemisphere tournament.
RugbyWA called talks with the ARU "unsatisfactory", saying they highlighted "that the terms of the assessment and process being used to evaluate ourselves and the Rebels were inconsistent and inequitable".
It added that "we felt in order to protect our position it was necessary to issue legal proceedings to protect our rights under the Alliance Agreement".
Under the agreement struck last year, Force players and professional staff became employees of the ARU after the governing body helped bail out the club, which was suffering financial problems.
According to the West Australian newspaper, the Force have a clause in the agreement that commits both parties to a current broadcast deal that ends in 2020.
The Australian newspaper cited Rebels owner Andrew Cox as saying his team may also go down the legal route.
The growing backlash follows Super Rugby's governing body SANZAAR announcing on Sunday that two South African teams and one from Australia would be axed, streamlining the 18-team competition to a three-conference 15-team format.
SANZAAR has left it to the national rugby unions involved to announce the teams to cut.
The ARU on Monday said it would be either the Force or Rebels, meaning the ACT Brumbies, NSW Waratahs and Queensland Reds were safe, with Japan's maligned Sunwolves joining the Australian conference.
ARU chairman Cameron Clyne previously said a decision would be made within days following an analysis of financial sustainability, performance and commercial factors.
But the deadline has now been pushed back.
"We maintain our commitment to reaching resolution on this matter as soon as possible, however the timeline that we initially anticipated of 48-72 hours will not apply," Clyne said on Tuesday.
The fallout has seen calls mount for ARU chief executive Bill Pulver to step down, with former Wallabies coach Alan Jones saying the entire board should quit over their handling of the issue.
"I can't comprehend how an Australian rugby administration would not stand up to SANZAAR and protect the interests of Australian rugby, not Japanese rugby," he told New Zealand's Radio Sport.
"To wipe out an Australian team and admit a Japanese team into the conference is mind boggling."