Former Berkshire Hathaway executive David Sokol's trading in Lubrizol shares as he pitched the company to Warren Buffett is a blurring of personal and professional profit-seeking that could attract a hard look from regulators.

Sokol presented a steadfast defense on Thursday.

He spent more than 30 minutes on CNBC to say he had no inside information, did nothing unlawful or unethical, and his resignation had nothing to do with his trading.

I didn't know anything others don't know, Sokol said.

Some experts, however, say he did know that he was pushing the Oracle of Omaha to buy a company he had a personal stake in -- something that could cause the shares to skyrocket if it leaked to the public.

Also, he may have had a duty to not take personal advantage of confidential information he gained as a result of his employment with Berkshire -- a key element of insider trading cases.

He has got an insider-trading problem almost certainly, said Gordon Smith, a law professor at Brigham Young University. This is a textbook example.

The SEC has not indicated whether it plans to investigate Sokol for insider trading, and Sokol himself said on Thursday during the interview that he has not been contacted by the agency. SEC spokesman John Nester declined comment.

Sokol was seen by many investors as the most likely successor to Berkshire Hathaway's iconic CEO, but Sokol said he did not aspire to the job and wanted to build his own mini-Berkshire instead.

Buffett released a letter on Wednesday disclosing that Sokol actively traded in a substantial amount of Lubrizol shares before and while urging Buffett to acquire the company, which Buffett did for $9 billion this month.

Sokol appeared to have made a profit of at least $2.98 million on his investment.

Lubrizol's chief executive, in a regulatory filing on Thursday, said the news would have no effect on the deal and that Lubrizol hoped to close the sale as quickly as possible.

COULD BE GRAY AREA

Sokol's move to purchase shares knowing that Lubrizol could be a viable acquisition target could constitute a breach of fiduciary duty to Berkshire because he acquired the information in the course of his employment.

This may be a gray area because Sokol said on Thursday that he thought it was an outside chance that Berkshire would buy Lubrizol, despite his eventual success in persuading Buffett.

If he knew that Berkshire is truly interested in the company, then he could be misappropriating information from Berkshire and that could amount to insider trading, said John Coffee, a professor of law at Columbia University.

Coffee said Sokol was reckless, but said it's far from a slam-dunk insider trading case.

Robert Thompson, a law professor at Georgetown University, said the fact that Sokol disclosed the stock holdings to Buffett at the time he pitched the deal could also be his saving grace.

If you disclosed it, you haven't committed a misrepresentation, he said. You have told the truth.

Potential SEC scrutiny may not be Berkshire's only headache. A well-known securities class action lawyer said on Thursday that institutional investors have already been in touch on the disclosures.

The timing and the facts surrounding the transaction have justifiably raised an interest and concerns from three of my clients, said Darren Robbins, a partner in the firm Robbins Geller Rudman & Dowd.

SOKOL CONCEDES APPEARANCE OF AN ISSUE

Sokol, in his interview on CNBC, spoke of broader Berkshire practices that could fuel lawsuits or regulatory scrutiny.

He said other Berkshire executives have in the past held stock in companies they then identified for investment or acquisition, citing the example of Berkshire Vice Chairman Charlie Munger owning a stake in Chinese car maker BYD <1211.HK> before suggesting it for an investment.

Nonetheless, Sokol, the chairman of Berkshire units MidAmerican Energy and NetJets said he understood how the sequence of events looked, even if he did nothing wrong.

I can understand the appearance of an issue ... That's why we made it public, he said.

Sokol resigned March 28. He said Buffett did not try to talk him out of resigning. Buffett's letter included an excerpt of Sokol's letter, but Sokol's full letter was not public.

Berkshire did not immediately return an email request seeking comment.

Berkshire's Class B shares, which are more heavily traded than its Class A stock, fell 2.1 percent to $83.63.

(Reporting by Sarah N. Lynch, Ben Berkowitz and Jonathan Stempel; Editing by Dave Zimmerman, Gary Hill, Phil Berlowitz)