The Delaware Court of Chancery has rejected Enbridge Energy Partners' bid to dismiss a shareholder suit targeting a $1 billion pipeline buyback deal, in a ruling that criticized the defendants for remaking arguments that had already been rejected by the state Supreme Court.

Vice Chancellor Joseph R. Slights III on Wednesday said EEP, a Delaware master limited partnership, had “returned to the well” in trying to dismiss the suit after the state high court revived derivative claims for breach of contract last March and sent the case back to Slights with “clear instructions” on how to proceed.

In a 48-page memorandum opinion, Slights slammed the “redundancy” of EEP's renewed motion and allowed the bulk of the plaintiffs' derivative claims to continue.

“Notwithstanding these clear instructions, defendants bring motions to dismiss the current version of the complaint on many of the same grounds our Supreme Court has already rejected,” Slights said. “Those grounds will find no revival here.”

Slights' ruling was the latest development in a series of legal challenges related to the fallout from EEP's $1 billion repurchase of the Alberta Clipper pipeline from its controlling parent in 2015. The move sparked outrage from EEP investors, who said EEP had sold the same pipeline, which carried petroleum from western Canada's oil sands to the United States' Midwest, at a significantly lower price in 2009.

Slights dismissed the complaint in May 2016 for failing to plead allegations of bad faith to overcome the built-in protections of a limited partnership agreement. However, the Supreme Court last year overturned the decision in a ruling that rejected the court's own rigorous bad-faith pleading standard for conflicted transactions.

Rather, the justices said, the plaintiff needed only to plead facts supporting an inference that the general partner did not reasonably believe it was acting in the best interests of the partnership, in order to survive a motion to dismiss.

The plaintiffs have since substituted a new party to lead the class and amended their complaint.

On Wednesday, Slights ruled that the essential investor pleading had remained unchanged. EEP, he said, had simply re-upped their earlier position that the plaintiffs had failed to plead demand futility and that those rulings “cannot and will not be revisited.”

“The well-pled facts in the first complaint upon which the Supreme Court rested its decision remain in the [third amended complaint] and, contrary to defendants' suggestion, they are not somehow 'unpled' by the additional facts pled in the [third amended complaint],” Slights said.

Attorneys from both sides were not immediately available to comment on Thursday.

Lead class plaintiff Judy Mesirov is represented by attorneys from Friedlander & Gorris and Rosenthal, Monhait and Goddess in Wilmington and Bragar Eagel & Squire in New York. Morris, Nichols, Arsht & Tunnell and the firm Paul Hastings in New York represented Enbridge, EEP and the director defendants.

The case is captioned Mesirov v. Enbridge Energy.