SAN FRANCISCO – A new law makes possessing up to an ounce of marijuana in California no more serious than getting a speeding ticket — a development both sides battling over a marijuana legalization ballot measure hope to exploit with the vote just a month away.

The law signed late Thursday by Republican Gov. Arnold Schwarzenegger reduces possession of an ounce or less of pot from a misdemeanor to an infraction with a maximum punishment of a $100 fine.

As a misdemeanor, possession of up to an ounce was punishable by only a $100 fine and no jail time. But offenders also faced arrest, a possible court appearance and a criminal record.

Schwarzenegger reiterated his opposition to the ballot measure known as Proposition 19 when he signed Senate Bill 1449 but said the new law would save the state courts money.

Other opponents of Proposition 19 said the new law helped their cause by negating the argument that legalizing pot would let police focus on more dangerous crimes, said Roger Salazar, a spokesman for the No on Prop 19 group.

Meanwhile, backers of Proposition 19 called the new law a step in the right direction but said the ballot measure was still needed.

Proposition 19 would more or less make the new law irrelevant by legalizing possession of up to an ounce for personal use for adults 21 and older.