Visitors arriving at the Isle of Man without the correct paperwork during the coronavirus pandemic have been turned away on 10 occasions, the government has said.
Those involved had travelled to the island both by ferry and plane without travel exemption certificates.
The island remains closed to non-residents without special permission.
The latest to be turned away was a couple from London who arrived at Ronaldsway Airport on Friday evening.
The pair were quarantined until the next available flight back on Sunday.
Isle of Man Constabulary said the couple had made a “genuine mistake” and would not face criminal charges.
A spokesman for Loganair, which operated the flight from London City Airport, insisted entry permit checks were carried out for all passengers on flights to the Isle of Man at both the check-in desk and the boarding gate.
The airline offered no explanation for how the couple may have slipped through.
Any non-residents arriving unable to produce an exemption certificate are dealt with by police.
Supt Steven Maddocks said the force takes a “sensible approach” to whether or not to prosecute those who breach the rules.
“The legislation does allow for people to be in essence turned around and sent back,” he said.
“If someone’s made a genuine mistake potentially they could be criminalised for making a mistake.”
He added that the problem could be eased if carriers made more thorough checks at UK ports, although there is no obligation for them to do so.
A government spokesman said passengers were “generally advised” about the requirement for exemption certificates at the point of departure.