Publicans have been reminded that if they allow any customers to smoke cannabis on their premises they are breaking the law.
New police guidelines were released this week highlighting the laws surrounding cannabis use.
Press reports suggested the drug was as good as legal, which has led some publicans to think this will encourage people to smoke it in pubs.
Dean Temple, licensee of the Barley Mow in Long Lane, London, said: "There is confusion among the general public. You get people who hear the news that there has been a change in drug policy from their mates. They don't know the full story and think it's legal.
"The whole thing is a pain for us. Customers have been caught smoking it in my pub before by the police. Some police officers are ok with us but there are others who say it's my licence and I have to sort it out. To be honest I need their help sorting out the problem."
The Association of Chief Police Officers (ACPO) drew up the new guidelines following home secretary David Blunkett's decision to reclassify cannabis from Class B to Class C status.
This decision, which was brought in last year, also caused confusion with pub customers, who thought the drug had been made legal.
While the new guidelines recommend greater flexibility and discretion for police officers, smoking cannabis in public is still an arrestable offence.
A spokesman for ACPO said: "The drug has been declassified but not decriminalised. It is still illegal. Now it will be much less of a policing priority.
"There are no specific guidelines for how a police officer should act if they catch someone smoking on licensed premises.
"What the guidelines do however is give the officer a chance to use his or her discretion.
"If an officer catches someone smoking the drug in a pub and there are families or children around, or a similar incident has taken place in that pub before, then the officer may wish to interview the licensee and take action. If it is an isolated incident then the officer might well leave the licensee out of it."
Mark Hastings, spokesman for the British Beer & Pub Association, said the legal position was quite clear for publicans.
He said: "This is no way changes the duties of the licensee to behave in a responsible way. The bottom line is cannabis is still an illegal substance."