The Delaware Court of Chancery on Monday decided that a deal to transfer full interest in companies owning and operating two pieces of natural gas infrastructure was so flawed as to cost common unitholders in the partnership that bought the companies $171 million.

Vice Chancellor J. Travis Laster, in a memorandum opinion in In re El Paso Pipeline Partners Derivative Litigation, said a committee representing the interests of El Paso Pipeline Partners did not adequately look into the benefits of the transaction to its investors. The flawed inquiry, Laster said, amounted to a breach of the duty owed by the general partners in El Paso Pipeline Partners to those holding a common equity stake in the company.