There's two different types of laws in play. One has to do with already accrued and vested pensions. Under federal law those are tangible property that can't be

There's two different types of laws in play. One has to do with already accrued and vested pensions. Under federal law those are tangible property that can't be adjusted outside of bankruptcy. Separately some states, including NY, IL, and CA have state constitutional doctrines that forbid changing the accrual formula for existing employees. This is much more stringent rules, and means that any change will take many decades to work through the system.