Talk about a clash of cherished green values.

In a case with statewide significance, the Santa Clara County District Attorney's Office is pursuing a Sunnyvale couple under a little-known California law because redwood trees in their backyard cast a shadow over their neighbor's solar panels.

Richard Treanor and Carolynn Bissett own a Prius and consider themselves environmentalists. But they refuse to cut down any of the trees behind their house on Benton Street, saying they've done nothing wrong.

"We're just living here in peace. We want to be left alone," said Bissett, who with her husband has spent $25,000 defending themselves against criminal charges. "We support solar power, but we thought common sense would prevail."

Their neighbor Mark Vargas considers himself an environmentalist, too. His 10-kilowatt solar system, which he installed in 2001, is so big he pays only about $60 a year in electrical bills. He drives an electric car.

Vargas said he first asked Treanor and Bissett to chop down the eight redwoods, which the couple had planted from 1997 to 1999 along the fence separating their yards. Later, he asked them to trim the trees to about 15 feet.

"I offered to pay for the removal of the trees. I said let's try to work something out," Vargas said. "They said no to everything."

He installed the panels.

district attorney arguing that the trees reduce the amount of electricity he can generate. In 2005, prosecutors agreed.

They sent Treanor and Bissett a letter informing them that they were in violation of California's Solar Shade Control Act and that if they didn't "abate the violation" within 30 days, they would face fines of up to $1,000 a day.

Obscure law

The law, signed by former Gov. Jerry Brown in 1978, is rarely used. But county prosecutors say Treanor and Bissett are breaking it.

"It's not that we think trees are more or less important than solar collectors. It's that our state's leaders have said under the following circumstances, solar takes precedence," said Ken Rosenblatt, supervising Santa Clara County deputy district attorney for environmental protection.

The law was written by former Assemblyman Chuck Imbrecht, a Ventura Republican, as a way to guarantee, amid the energy crises of the 1970s, that people who installed solar panels wouldn't see a drop in their investment from nearby trees.

It affects only trees planted after 1979, and bans trees or shrubs from shad