WILMINGTON, Del. — A Delaware judge on Monday dismissed a shareholder lawsuit alleging that billionaire Warren Buffett and directors of Berkshire Hathaway Inc. failed to take proper action in response to stock trades by a former Berkshire executive ahead of the company's $9 billion acquisition of chemical manufacturer Lubrizol.

Vice Chancellor J. Travis Laster ruled that the shareholders failed to demonstrate before filing their lawsuit, as required by Delaware law, that the Berkshire board was not capable or willing to take legal action itself, or that it would be futile for shareholders to demand that it do so.

The shareholders argued that the Berkshire board has been sitting on its hands for more than a year since the executive, David Sokol, resigned. But Laster suggested there could be entirely proper reasons why the board has delayed a decision on whether to sue Sokol, including a pending investigation by the Securities and Exchange Commission.

"It's not clear to me that it's obvious that one should go after him now," said Laster, adding that he could not conclude based on the pleadings submitted to him that the close relationship between Buffett and Sokol was "board-disabling."

Laster dismissed the shareholder lawsuit without prejudice, however, meaning the plaintiffs could file a complaint later if circumstances warrant.

"If somebody isn't doing something with a litigation asset that looks particularly strong, you have to wonder," the judge said. "... There's some smoke here."

A spokeswoman for Berkshire Hathaway did not immediately respond to email and telephone messages seeking comment on dismissal of the lawsuit.

According to court records, Sokol bought 2,300 shares of Lubrizol in December 2010, one day after he asked a Citigroup investment banker to contact the CEO of Lubrizol about possible deal talks. Sokol sold those shares a week later, then bought nearly 100,000 Lubrizol shares in early January 2011 for about $100 a share, even though he knew Lubrizol's board had been discussing Berkshire's possible interest in acquiring the chemical company.

About a week after Sokol bought his Lubrizol shares for about $10 million, he talked to Buffett about Berkshire acquiring the company. Buffett has said Sokol mentioned only in passing that he owned Lubrizol stock, and that he didn't learn the details of the transactions until shortly after the deal was announced. Berkshire's offer of $135 in cash for each share of Lubrizol meant Sokol's shares increased in value to about $13 million.

Attorneys for Berkshire noted Monday that Berkshire voluntarily released details of Sokol's trading activities in a March 2011 announcement of his resignation. The company's audit committee also issued a harshly worded report a month later saying Sokol had violated his "duty of candor" in not fully disclosing details of his Lubrizol trading to Buffett and Berkshire Chief Financial Officer Marc Hamburg.

The audit committee authorized Buffett to release its report publicly, saying it would send a message that employees must abide by Berkshire prohibition against insider trading and adhere to its code of business conduct and ethics. The committee also said Sokol had suffered a "severe consequence" related to severance benefits because of his voluntary resignation.

The committee said that the board was considering whether to take legal action against him to recover his trading profits or any damage suffered by the company.

The shareholders, who filed their initial lawsuit before the audit committee had even released its report, argued that the company should have done more. They sought damages on behalf of Berkshire from Sokol and the company's directors, and "disgorgement" or surrender, by Sokol of some $3 million in profit he realized in the Lubrizol takeover.

"He walked," said plaintiffs attorney Robert Weiser, adding that Sokol, who was chairman and CEO of NetJets Inc., a Berkshire subsidiary, is receiving a million dollars a year in retirement benefits from MidAmerican Energy Holdings Co., another Berkshire subsidiary that he led.

Sokol's attorneys argued that the Delaware court did not have jurisdiction over their client because Sokol, once considered a likely successor to Buffett, was never an officer or director of Berkshire Hathaway.

Attorneys for the shareholders argued in opposing dismissal of their complaint that Sokol had held himself out as a "defacto" officer of Berkshire and that he owed a fiduciary duty to the company.