A number of Irish passengers, who travelled with a negative test or on their HSE vaccine card, are being made quarantine in hotels in Malta.
Six people have been placed in mandatory quarantine as the country does not accept a negative test.
Malta is also not accepting a COVID recovery cert, a COVID vaccination cert with one dose, or vaccine certs with less than 14 days from the final dose.
Travel expert Eoghan Corry told Pat Kenny Malta is the exception to the rule on this.
"You are allowed in with a Digital COVID Certificate... if you have that on your phone, you've no restrictions travelling into Malta.
"Malta's a bit different to other countries: they don't accept a test - that means no antigen, no PCR.
"They also said they don't want children; there's quite a few people listening this morning [who] would probably see that as a bonus."
But he says a number of Irish travellers, who arrived in Malta on Tuesday, were turned away.
"Six people arrived off the flight from Dublin and they didn't have the Digital COVID Certificate with the QR code, but they had the vaccination card.
"This is reflective of what's been happening across Europe - there's been an acceptance that Ireland has a lot of people waiting for the e-mail with the code, and they have been through the full course of vaccination.
"People have been getting into Spain, Portugal, Greece, Italy with the card signed saying 'This is your vaccination date and this is the batch number'.
"Malta are not doing that - so the six people who arrived on the flight, instead of the Digital COVID Certificate, they had the card signed - they were told 'Not here'.
"So they've gone into mandatory hotel quarantine, and now they can re-book a flight but they will be escorted and watched and put back on the flight.
"And of course they're subject to the re-entry negotiations when they come to Ireland.
"It all relates to the slow rollout of the Digital COVID Certificate - this wouldn't have happened if they'd all been delivered in time.
"And the second thing is Malta is an aberration to what's been happening right across Europe."