The Delaware Court of Chancery on Tuesday ruled that a challenge to natural gas company Regency GP’s 2015 merger with Energy Transfer Partners had cleared a preliminary hurdle to show that Regency’s board may have approved a deal that it knew was not in the firm’s best interest.

The ruling, from Chancellor Andre G. Bouchard, left just one claim standing after a second attempt by Regency and ETP to extinguish the case, which centers on protections for master limited partnerships. The suit’s other three counts were dismissed as inconsistent with state law governing limited partnerships.