In M&G Polymers USA v. Tackett the Supreme Court held unanimously that ordinary principles of contract law apply to determining whether lifetime contribution-free retiree health insurance benefits are vested or terminate when the collective bargaining agreement (CBA) expires. The CBA in this case said that those who retire at a certain age with certain years of service “will receive” fully paid for health insurance.  When the CBA expired M&G announced that retirees would have to contribute to the cost of health insurance.  The Sixth Circuit agreed with the retirees, applying the Yard-Man inference from a 1983 Sixth Circuit decision, that the retiree benefits vest for life.  Justice Thomas, writing for the Court, criticized the Yard-Man inference on many grounds but most fundamentally that it “violates ordinary contract principles by placing a thumb on the scale in favor of vested retiree benefits in all collective-bargaining agreements.”  This case was decided under the federal Labor Management Relations Act, which does not apply to state and local governments.  But the same question arises under public sector CBAs, and arbitrators and courts may look to this decision for guidance.