Faced with opposition from drug legalization advocates, California lawmakers backed away Tuesday from a proposal to adopt a “zero tolerance” policy on motorists under age 21 who drive after using marijuana.

A bill by state Sen. Jerry Hill (D-San Mateo) originally proposed a one-year suspension of driver’s licenses for minors caught for the first time driving with measurable amounts of marijuana in their system. Hill had said the state should have the same “zero tolerance” policy for cannabis that it has for those under 21 who drive under the influence of alcohol.

But faced with opposition, Hill agreed on Tuesday that the first offense would result in a warning, and the second offense would add one penalty point to the driver’s record, removable if they take a drug-awareness class. Only the third and subsequent offenses would result in suspension of the driver’s license.

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The Senate Public Safety Committee recommended the amended bill with votes withheld by Democratic Sens. Holly Mitchell of Los Angeles and Steven Bradford of Gardena. The two lawmakers shared a concern that minority drivers would be disproportionately targeted by law enforcement.

“I think this is a slippery slope to target people of color,” Bradford said.

Sen. Nancy Skinner (D-Berkeley), the committee’s chairwoman, said she supported making the bill “a little more benign,” adding there is no “zero tolerance” policy for distracted driving, which she said causes more accidents by young people than do drugs.

Opponents included Glenn Backes, a lobbyist for the Drug Policy Alliance, which supported a measure that legalized the sale of marijuana for recreational use starting Jan. 1.

Backes said the oral swab saliva test proposed to determine the presence of delta-9-tetrahydrocannabinol has been known to produce “false positive” results.

“The tests that are being mandated in this bill are unreliable,” Backes told the committee.

The bill was also opposed by Mica Doctoroff, an attorney for the ACLU of California, who said the penalties — including suspensions and fees — are “too onerous,” and also said she is concerned they would disproportionately affect African American and Latino drivers.

“The uneven enforcement of California’s traffic laws on black and Latino drivers is very well established even though there are no documented differences in the driving behaviors of black, Latino and white drivers,” Doctoroff told the senators.

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Sen. Joel Anderson (R-Alpine) was the only vote against the bill. He said he is concerned about innocent bystanders being cited after breathing secondhand marijuana smoke.

“I never smoked marijuana, but I went to a reggae concert once,” Anderson said.

Hill said it is unlikely those levels would register in the test.

He said the penalty for drugged driving is necessary, noting that 3.5% of minors killed in traffic accidents in 2013 in California had marijuana in their system, but the number jumped to 15% two years later.

“It shows that there is a problem,” he told his colleagues.

Students from UCLA and North High School in Torrance testified in favor of the bill and said their peers do not realize the danger of being impaired while driving after using marijuana.

The measure also was supported by retired California Highway Patrol Lt. Robert McGrory, whose son, CHP Officer Justin McGrory of Victorville, was killed by an 18-year-old who had been smoking marijuana before he got behind the wheel of his car.

“We have to educate the young,” McGrory told the panel.

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