The ban, which is similar to those given out to mischievous school children in shops, has been enforced after a series of incidents in the last week.
A notice posted on the door of The Harbour Fish and Chip Shop in Lerwick, Shetland said the rule was due to a number of men misbehaving.
And the restrictions have now been placed on workers from Morrison Construction, Petrofac and Wood Group PSN.
The three companies have hundreds of employees on the islands as part of the Shetland Gas Plant project.
It is understood that a man had made several offensive remarks directed at staff on Friday and then on Sunday a fight broke out among six men in the chip shop.
The manager of the shop, who did not wish to be named, confirmed the two incidents had happened but declined to say anything further.
A spokesman for Petrofac said: “We take our responsibilities to the Shetland community extremely seriously and make every effort to impress them on our staff and those of our contractors.
“This includes strict guidelines for appropriate behaviour on and off-site. If we find evidence that these guidelines have been breached then appropriate action will be taken.”
A Morrison Construction spokeswoman said: “While we have received no direct reports that our own operatives have been involved in any recent incidents, Morrison Construction takes the behaviour of its staff and their conduct within the wider community very seriously.
“As a result we are reiterating to all of our operatives in Lerwick the standard of behaviour expected of them and we will not tolerate any actions that cause distress to the local community.
“We will continue to strive to maintain good relations with the wider community wherever possible and ask anybody who does have a concern to contact us as soon as possible.”
A spokeswoman for the Wood Group added: “Wood Group PSN respects all the communities in which we operate and any breach of acceptable behaviour by our workforce would result in us taking appropriate action.”
A police spokesman said: “On Monday 15 June at 9.11 am, police in Lerwick received a report of a disturbance which occurred at 10.50pm on Sunday 14 June within a commercial premises on the Esplanade in Lerwick.
“At around 11.40 am on Monday 15 June, police in Lerwick received a report of a separate incident of verbal abuse towards a staff member within the work place at the same commercial premises in Lerwick.
“This incident occurred at around 10.20 pm on Friday 12 June.
“Enquiries remain ongoing to the incidents. If anyone has any information regarding either incident they are encourage to contact police via the non-emergency number 101.”