The grassroots lobbyists who pushed the Virginia General Assembly to pass tougher drunken-driving laws are moving their troops from the statehouse to the county courthouses.

Encouraged by their victory with the legislature, their next targets are the judges charged with enacting the reforms, spokesmen for the citizens' organizations say.

"The General Assembly was just the beginning for us," said Edward J. Kunec, president of the Northern Virginia parents group, Mothers Against Drunk Drivers (MADD).

The Northern Virginia group and dozens like it across the state are credited with waging one of the most effective citizens' campaigns for law reform in recent legislative history.

The MADD organizations and their offshoots, Students Against Drunk Drivers (SADD), sprang up almost overnight throughout Virginia in response to a number of teen-age fatalities attributed to drunken drivers. In less than six months, their memberships have swelled into the hundreds.

They plied lawmakers and state executives with thick petitions, heart-twisting testimony and grueling persistence.

And the results of their crusade surprised many legislators.

"They had a very substantial effect," said Del. James H. Dillard (R-Fairfax). A new law setting mandatory jail sentences for repeat offenders was "stronger than what I expected," added Dillard, an advocate of tough penalties for driving drunk.

But Dillard warns that the fight is far from over.

"It will require a constant vigil on the part of the public to make sure judges are not simply letting people off," he said.

MADD and SADD groups say they will station representatives in courtrooms throughout the state.

"We want to see if they're responsive to the new laws," said Kunec, whose 20-year-old son died last July from injuries he received when he was struck by a car driven by a drunk. "If they are not, we will confront them."

Kim Ritchie, a sophomore at Woodson High School in Fairfax County and one of the organizers of the first SADD groups in Northern Virginia, said high school students will be monitoring courtrooms throughout their summer vacations.

A major criticism of Virginia's drunken-driving laws, voiced during many of this year's legislative hearings, was that the real problem lies with the judges. Current law authorizes judges to impose jail terms of up to six months for a first offense, but the full penalty is seldom imposed, according to critics.

Judicial discretion with repeat offenders is sharply restricted under the new law, which requires at least 48 hours in jail for a second offense, as well as a one-year license suspension. Persons convicted of drunken driving a third time would receive one month in jail and a lifetime revocation of their licenses.

The new law also rescinds a provision that has allowed offenders to avoid conviction by completing a state-run alcohol education course.

The final version, however, is still weaker than the original legislation backed by the MADD and SADD groups. That bill would have required a jail term for the first drunken-driving conviction. Sen. A. Joe Canada (R-Virginia Beach), who sponsored that measure, accused the defense lawyers who dominate the House Courts of Justice Committee of scuttling his bill.

But citizen activists say they aren't disappointed.

"We didn't go down there with a strong feeling that we would conquer the world the first time around," said Kunec, adding it was the first venture into politics for most of those who lobbied the issue.

But many legislators, including Dillard, say it won't be easy to keep the momentum of the successful crusade going.

"Obviously, these groups are formed for a specific purpose," Dillard said. "If that is achieved, they have to change their cause or die."

Kunec argued that the MADD and SADD organizations have a strong incentive to stay alive. "Before, people like us grieved by themselves," he said. "Now we can bring about an awareness that the people who are grieving have been victimized."