HARRISBURG, Pa. (AP) — Coal-related interests are suing to block the centerpiece of Gov. Tom Wolf’s plan to fight climate change, a carbon-pricing policy that will impose a cost for emitting planet-warming carbon dioxide from fossil fuel-fired power plants. The lawsuit filed Monday in Commonwealth Court by owners of coal-fired power plants, owners of coal mines and labor unions say the regulation written by Wolf’s administration is unconstitutional. The regulation took effect Saturday. It made Pennsylvania the first major fossil-fuel state to adopt a carbon-pricing policy. Wolf, a Democrat, is already fighting one lawsuit intended to block the regulation and maintains the state can regulate carbon dioxide under existing air pollution laws.