The Delaware Court of Chancery has dismissed a $428 million shareholder derivative suit accusing The Williams Cos. Inc. board of using a planned $13 billion acquisition to torpedo the company’s doomed merger with Energy Transfer Equity.

Williams investor Walter E. Ryan Jr. said the board of the Toledo-based energy firm had initially pursued the $13 billion purchase of its own master limited partnership, Williams Partners, as a defensive measure to fend off Williams’ proposed $38 billion tie-up with ETE—only to later pull the plug on the deal and then watch the blockbuster merger with ETE fall apart.