SACRAMENTO, Calif. (KGO) -- San Francisco Assemblywoman Fiona Ma joined a coalition of supporters in Sacramento Tuesday to promote a new bill that would make it harder for teenagers to buy alcohol at the supermarket.

The grocery industry says its customers love self-serve checkout stands and there's no evidence the new technology helps kids buy alcohol, but a growing movement says it does.

More and more grocery stores are using self-serve checkout stands. At Fresh & Easy, the registers are completely unmanned with a worker nearby for help. At certain times, though, minors are able to buy alcohol, even though the self-serve stands are supposed to freeze and alert workers to check the customer's I.D.

"When the store is really busy, it's just impossible to keep track of what's going on with all those registers," says Fresh & Easy customer assistant Lisa Austin.

There are ways to cheat the system by quickly scanning the next item or sliding a credit card for payment before the freeze happens. There also have been instances when a six-pack of soda is scanned, but a six-pack of beer is bagged.

A 2009 UCLA study found 20 percent of young adults were able to buy booze by tricking the self-checkout system. Ma, a Democrat, wants to bring back face-to-face interaction to alcohol sales, just like cigarettes.

"My bill simply requires that alcohol be purchased through a sales clerk and not a self-checkout machine," says Ma. "It is better to be safe than sorry."

The grocery industry says there's no correlation between self-serve checkouts and minors buying alcohol, citing a recent study by the California Department of Alcoholic Beverage Control.

"Retailers will do anything they can to protect those liquor licenses," says Ron Fong of the California Grocers Association. "They're not going to sell to underage minors."

Critics also point out this bill is backed by the United Food and Commercial Workers union, which is fighting to save jobs threatened by new technology. But the proposal is also supported by law enforcement and Mothers Against Drunk Driving.

"What a horrific sight that I have in my mind," says Irene Rubalcaba who lost her granddaughter to an under-aged drunk driver. "I just don't want another child or another family to endure what my family has gone through."

Ma's bill will be up for a Senate committee vote later this month. It's the same committee that killed the proposal once before.