Other Dunedin businesses had also been offering drinks to customers, including a nail salon, which offered a glass of wine to customers as part of a Christmas special last year, Paulin said.
Rather than prosecuting the businesses, Paulin told the operators about their legal obligations.
He pointed out that although the drink was offered as complimentary, it was only provided when customers paid for other services, which effectively meant businesses were selling alcohol without a licence.
A spokeswoman for Loft Hair, in Crawford St, Dunedin, disagreed.
She said her salon offered a complimentary small glass of wine to customers, and believed it created a "nice relaxing afternoon experience".
"Personally, I think as long as you're serving one drink per person, it shouldn't be a problem.
"I almost think they're the fun police rather than the Dunedin Police.
"It's ruined it for everybody.
"It should be up to the individual.
"I was always under the impression that as long as we weren't selling a glass of alcohol, then we'd be fine.
"I disagree with the fact that if you're providing a service, you're selling a drink. I disagree 100 per cent."
Although she disagreed with the liquor licensing law, she said Loft Hair would no longer offer alcohol because she did not want to get in trouble with the police.
Bloke owner Keri O'Connor said she worked in hairdressing in the late 1980s and 1990s, and it was common for customers to be offered an alcoholic beverage.
It was allowed under the former Sale of Liquor Act 1989, and some people have continued to do it under the new Sale and Supply of Alcohol Act 2012, which made it illegal.
O'Connor said Bloke offered complimentary beer to customers if they were over 18 and not intoxicated, but she had stopped the practice after a visit from Paulin.
"I do think you should be allowed to give a beer to someone who has finished working for the day and is sitting relaxing.
"But unfortunately, it is the law that you can't do it.
"So we're taking it on the chin and stopping because I don't want to be prosecuted.''
Spokesmen for Barkers Groom Room Dunedin and head office in Auckland declined to comment.
Paulin said offering one drink to customers was not harmless.
"It's clearly illegal and that's the bottom line.
"It doesn't say anywhere in the Sale and Supply of Alcohol Act that harm has to be caused by infringing [the Act]."
Dunedin businesses were among several around the country that police have told to stop the practice.
National prevention manager Inspector Paula Holt said police were aware some service outlets, including hairdressers and barbers, had been advertising complimentary alcoholic drinks.
As a result, police had contacted a number of businesses to let them know the practice was illegal, she said.
Police did not intend to pursue the matter any further than providing guidance to business owners at this stage, she said.
But if businesses ignored calls from police to stop offering alcohol to customers, they faced punishments of up to three months in prison and a $40,000 fine.
