The company, now called CNH American and based in Pennsylvania, also must reimburse those covered by the lawsuit for medical expenses incurred while the company was not paying 100 percent. The suit covered workers who retired prior to 1994.
A lawyer explained the ruling to about 40 retired Case workers or their surviving spouses last night, according to The Tribune-Star of Terre Haute.
The lawsuit stems from an agreement between the farm and construction equipment maker and the United Auto Workers Union that promised retirees health care coverage the rest of their lives.
But the company began charging premiums for coverage in 2002 and increased that premium over the next two years, which retirees said was a violation of the agreement.
The Michigan judge said the company can't change the agreement even if costs grow higher than was expected when the agreement was struck.
The ruling affects workers at a number of plants around the country. The company no longer has a plant in Indiana.