Three public worker unions have been allowed to join a lawsuit against the Maine Public Employees Retirement System over the elimination of cost-of-living adjustments. A federal judge on Tuesday ruled that the Maine State Employees Association, Maine Education Association and Maine State Troopers Association can join the Maine Association of Retirees in its lawsuit filed in February. The 15,000-member retirees association sued the retirement system over the elimination of cost-of-living adjustments for three years and a new cap on cost-of-living increases after that. The unions say in the complaint that the elimination of cost-of-living adjustments for retired employees violated the Constitution as an unlawful taking of property without just compensation, and a violation of the contract clause. The retirement system says the elimination will save the state millions of dollars.