WASHINGTON (AP) — The Supreme Court has indicated it could throw out an $18 million penalty against a natural gas company convicted of an environmental violation in Rhode Island.In arguments Monday at the high court, several justices sounded skeptical of the government's case for upholding the penalty against Texas-based Southern Union Co. over its improper storage of mercury in a building in Pawtucket.But unlike other Supreme Court disputes involving corporations, this case does not appear to divide the justices along ideological lines.Instead, the court is focusing on a line of cases limiting judges' discretion to increase prison sentences. Southern Union says the same logic should apply to fines.The Obama administration says judges have much more discretion to hand out fines.