HARRISBURG — A constitutional challenge by seven municipalities to Pennsylvania's new law regulating the growth of natural gas exploration is in the hands of seven Commonwealth Court judges after a hearing Wednesday in which they repeatedly challenged lawyers from both sides in the closely watched case. The municipalities want the law overturned; the state wants the case thrown out. The judges also could ask for more evidence before making a final ruling or could strike down only parts of the law. Lawyers said they expect a ruling within several months. The heart of the argument is the extent of the state's power to tell municipalities where they must allow drilling-related activity, including rigs, waste pits, pipelines and the compressor and processing stations that help move gas from the underground Marcellus Shale formation in Pennsylvania to consumers across the northeastern United States. Among the objectionable provisions cited by the towns' March 29 lawsuit are requirements that drilling, waste pits and pipelines be allowed in every zoning district, including residential districts, as long as operators observe certain buffers. At one point, President Judge Dan Pellegrini asked a lawyer representing the Department of Environmental Protection and the Public Utility Commission what would happen if the state passes similar laws for every industry it considers an economic engine. “If you make that argument, pretty soon zoning becomes irrational,” Pellegrini said. The 174-page law established the first major levies on the Marcellus Shale industry in Pennsylvania — allowing counties to set an impact fee on the booming industry — and toughened some environmental and safety laws. Republican Gov. Tom Corbett signed the law Feb. 14 after his staff negotiated the final version behind closed doors with leaders of the Republican-controlled Legislature. The panel of seven judges includes five Republicans and two Democrats. Judge Anne E. Covey asked a lawyer for the municipalities how he can argue that the state is infringing on the municipalities' constitutional responsibility to protect its residents when the Legislature has the power to dictate the extent of those powers.