The brewer has joined forces with Dorset police to distribute posters to every off-licence and selected bus shelters in Dorset reminding people of the law as part of Project Blitz.
Buying alcohol for minors - known as "proxy purchasing" - carries a penalty of £80 and the risk of a court appearance and a £5,000 fine.
Sergeant Nikki Billington of Dorset police said: "It wasn't so long ago that young people could quite easily buy alcohol themselves, but things have changed somewhat over the last few years.
“With the introduction of proof of age cards and frequent test-purchasing operations, buying alcohol underage is no longer so easy. Consequently, young people are now more inclined to ask older friends or relatives to buy it for them."
Mark Woodhouse, vice chairman of Hall & Woodhouse added: “Producers and retailers of alcohol cannot ignore the issues that currently surround them. The vast majority of alcohol is consumed legally and responsibly, but we are very keen to play our part in the reduction of alcohol related anti-social behaviour."
At Clarkson's off-licence in Selsey, West Sussex, owner Denise Miles says she is well aware of the problem and is constantly reminding customers of the law surrounding proxy purchasing.
"The battle is certainly with the adults. I sometimes see youngsters waiting across the road asking adults to buy them alcohol, so if they come in I tell them 'if you buy it you could end up with a fine and losing me my licence'. People don't understand the law," she said.
Mid Devon police are also tackling the problem in their area by persuading drinks retailers to print "buying alcohol on behalf of under-18s is a criminal offence" on receipts and displaying an A4 poster reminding adults of the law in store.