Customers could not buy alcohol in automatic self-checkout lines under legislation sent Friday to Gov. Jerry Brown.

Supporters say the measure, Assembly Bill 183, would help protect public safety by ensuring that alcohol is purchased in face-to-face transactions in which a clerk can check identification and prevent sales to minors.

But officials of the grocery industry say the bill's real purpose is to minimize self-checkout stands and force grocery chains to hire more union clerks.

Self-checkout machines are designed to "lock-out" and stop if alcohol is scanned, but Assemblywoman Fiona Ma, a San Francisco Democrat who proposed AB 183, pointed to a study suggesting the safeguards are not always effective.

The Assembly passed the bill, 43-26, with most Democrats supporting it and most Republicans opposed.