BP Plc violated Texas's "revolving door" law by hiring a former state environmental engineer to work on the same air-pollution permit he'd supervised as a regulator, lawyers suing the company claim in court papers. The permit, which governs BP's Texas City, Texas, refinery, allowed the company to operate the installation without replacing outdated emissions controls, including one that exploded in March 2005, killing 15 workers and injuring hundreds. Texas law requires applications be rejected when the people involved worked on both sides of the permitting process. … BP has denied any improprieties in its air-permitting process at the refinery, its biggest.