SAN FRANCISCO — It started with a law firm "wine and dine" weekend to entertain a Silicon Valley client and ended in insider trading allegations from the Securities and Exchange Commission.

SEC enforcement lawyers in San Francisco accuse the husband of a Baker & Hostetler partner of using confidential information gleaned from his wife’s firm in 2011 to make nearly $30,000 in illicit profits.

The details of the complaint filed Wednesday in U.S. District Court in Houston illustrates just how easily confidential client information can leak and be used for personal gain, SEC officials said.

In this case, it was a last-minute change of plans by the general counsel of Santa Clara-based National Semiconductor Corp. that gave rise to the illegal trading charges.

The SEC accuses James Balchan, an IT specialist in Houston, of purchasing 3,000 shares in the semiconductor company after learning of its imminent acquisition by Texas Instruments.

Balchan and his wife had planned to attend a Baker & Hostetler social event organized to honor National Semiconductor’s GC on April 2 and 3, the complaint states. (The complaint doesn’t identify the GC, but at the time it was Todd DuChene, a Baker alum.)

As the negotiations with TI heated up, DuChene told a partner at Baker working on the deal that he wouldn’t be able to attend the social function. That partner told Baker lawyer Tonya Jacobs, who allegedly told her husband, Balchan, about the then-secret deal.

Following the announcement of the $6.5 billion deal April 4, 2011, the value of National Semiconductor shares jumped approximately 75 percent.

Balchan agreed to settle the case, paying roughly $60,000, without admitting the allegations. His attorney could not be reached for comment.

Balchan’s wife is not named in the complaint, nor is Baker & Hostetler. But public records show Balchan is married to Jacobs, who was employed by Baker & Hostetler from 1994 to 2012. Jacobs is no longer named on the firm’s site, and a firm spokeswoman did not return phone or email messages.

It is hardly the first time a law firm has been at the center of an insider trading case. In 2011, the SEC charged an attorney who worked at Wilson Sonsini Goodrich & Rosati with sharing information about mergers involving the firm’s clients. In 2009, an attorney at Ropes & Gray was charged with providing inside information on corporate transactions involving his firm.

Marc Fagel, director of the SEC’s San Francisco office, issued a statement reminding lawyers to be careful.

"Spouses or other members of an attorney’s family may learn highly confidential information about a company when having casual conversation," Fagel said. "Using that confidential information to buy or sell stock as Balchan did is not only a breach of trust, but also a violation of the federal securities laws."

Bingham McCutchen partner Raymond Marshall, co-chair of the firm’s white-collar investigations and enforcement group, called the scenario "all too common."

Attorneys must be disciplined about not discussing client matters in public, he said.

"All firms, including ours, have a very vigorous standard of not discussing client business outside the firm," Marshall said. "That means no elevator speak. No conversations to be overheard at lunch. No Super Bowl party chat about what you’re working on."