Underage drinkers will soon have a new enemy to contend with.

The state is encouraging liquor stores to buy scanning machines that check the validity of driver’s licenses, and at least one New Haven liquor store plans to buy one of the devices.

The governor signed into law last month an act that frees liquor stores from prosecution for selling to underage buyers if the stores use the scanners. State Sen. Bill Finch of Bridgeport, who co-sponsored the legislation, said the proposal was inspired by epidemics of fatal underage drunk driving.

“To present a phony ID and to get into the car with alcohol is not quite a loaded gun, but it’s pretty close,” Finch said.

But the scanning devices are so expensive — up to $2,400 — that many downtown liquor stores said buying them would not be worth it.

If caught selling alcohol to underage patrons, merchants can face fines up to $1,000, up to one year in prison or both. Still, liquor store owners, who said they have never or only occasionally been fined, said it was not worth it to buy the machines.

Eileen Fullarton, owner of Chapel Wine Shop, said she would love to purchase a scanner if the cost were not so prohibitive.

“If they start offering them with loans, I definitely will get one,” said Fullarton, who has a stack of confiscated licenses several inches thick.

Finch projected that the price of the machines will decrease as demand increases.

When a driver’s license or state-issued identification card is scanned, the machine will beep if the card is expired, the person is underage or the document is inauthentic. The machine does not work with cards from states that do not include magnetic strips.

If the license is genuine, but is presented by a buyer who is using someone else’s ID, liquor stores can still be prosecuted, so clerks still need to check the face on the license.

New Haven liquor store owners and employees said they knew very little about the new law, which goes into effect Oct. 1. They also said they have had very little trouble with fake IDs, using booklets with pictures of out-of-state IDs or asking for a second item of identification when the ID presented looks questionable.

But one liquor store will be buying the machine.

College Wine manager Sunny Patil plans to get an ID scanner in two or three weeks, though he only once incurred a $300 fine “five or six years back.”

“There are so many phony IDs around here,” Patil said.

By Connecticut law, individuals who misrepresent their age or use someone else’s identification can face fines between $200 and $500, 30 days in jail or both.

“There are going to be mad teenagers, but at least they’ll be alive,” Finch said.