When his lawyer called at 7:15 this morning to say he had shaken the U.S. government to its core, stereo salesman Jagdish Rai Chadha, 38, could think only of the day seven years ago when federal immigration agents treated him like a criminal.

Born in Kenya of Indian parents and holding a British passport, Chadha was attempting then to renew his application for permanent residence status. But when the immigration agents found out his student visa had expired, they fingerprinted him and didn't let him go until 6 p.m.

Determined to stay in America, Chadha began a legal fight that today, as a monumental byproduct, led the U.S. Supreme Court to strike down the often-used "legislative veto," possibly invalidating portions of more than 200 laws.

"It's kind of overwhelming," Chadha said in a telephone interview from his home in Berkeley, Calif. "To come to this after the way they pushed me around in L.A."

Chadha appealed the Los Angeles agents efforts to deport him until he finally got a favorable ruling from the Justice Department. When Congress vetoed that, he went to the federal courts.

Chadha said his court battle prevented him from finding the kind of job he wanted and he could not go to London to attend his mother's recent funeral.

Even when he married Terry, an American high school teacher, his lawyers "didn't like it because they thought it might invalidate the case." When he married an American citizen, he was legally entitled to stay in this country.

"I was joking with a friend of mine," said Chadha, as he took several phone calls and posed for photographers on his day off as assistant sales manager of Pacific Stereo in San Francisco. "I said that now, as long as the republic of the United States lives, the law students will all study my case."

San Francisco attorney John Pohlman saw the constitutional possibilities of Chadha's case, and represented him free. Washington attorneys Alan Morrison and John Sims also helped.

Sims to this day says he does not know why Congress vetoed Chadha and five others from a list of 350 aliens to be granted permanent residence status. It may have been because he had a British passport, "and deporting someone to Britain might not seem a hardship," even though Sims said East Indians suffer from discrimination there.

Chadha has a daughter, Sashi, 2, and his wife is pregnant. Terry Chadha became so impatient with the court delays that she wrote to Supreme Court Justice Sandra Day O'Connor, one of those who ruled in Chadha's favor today.

Chadha remains a little shocked at his wife's presumption: "I told her it wasn't the same thing as writing to your congressman."