A senior police chief has admitted the PSNI was still grappling with how to enforce the controversial 14-day quarantine as it came into force on Monday.
Assistant Chief Constable Alan Todd said the "practical details" of how the new rules will work is still being finalised.
From Monday, anyone arriving into the UK from abroad via plane, ferry or train is required to provide an address where they will self-isolate for 14 days.
The UK rules, however, do not apply to visitors from other parts of the Common Travel Area (CTA).
Fines of £100 can be issued to travellers who do not correctly fill in the required forms, with surprise visits by police potentially leading to fines of up to £1,000 in England for individuals breaking the rules.
In the rest of the UK, fines start at £60, reduced to £30 if paid early.
Repeat offences rise to a maximum of £480 in Scotland, £960 in Northern Ireland and £1,920 in Wales.
The regulations do not affect travel between Northern Ireland and the Irish Republic.
Overseas visitors arriving at Dublin Airport will be required to fill in a passenger locator form. But those heading straight to Northern Ireland do not have to state where they are staying to self-isolate.
It is still not known how information between the two jurisdictions will be shared.
Travellers arriving in the UK from within the Common Travel Area - which includes the Republic, the Isle of Man and the Channel Islands - will not need to self-isolate unless they have arrived in the CTA in the last 14 days.
This closes the so-called 'Dublin dodge', a loophole that would have allowed passengers to make a quick trip to the Irish capital and claim exemption.
The scheme has been met with widespread criticism from the aviation and tourism industries, which have warned the rules will cripple both sectors.
Mr Todd admitted work is still under way over how the scheme will be implemented by the authorities.
"The Health Protection (Coronavirus, International Travel) Regulations (Northern Ireland) 2020 have been published which impose requirements on individuals arriving in Northern Ireland from a country outside the Common Travel Area," he explained.
"We will be liaising with colleagues in the Department of Health and UK Border Force on the practical details of how they will be implemented."
The development comes as TUV leader Jim Allister criticised the lack of apparent preparedness by authorities here in implementing the new rules, which he stressed may be ineffective.
"There is something of a too little, too late feel to these proposals," he said. "They would have made more sense at the outset, but instead we kept receiving flights. Now, the greater danger to the UK from these proposals could be to the economy rather than from the virus.
"I also question how such could be policed, particularly with the Common Travel Area dimension."
His criticism comes as former World Health Organisation (WHO) chief Professor Karol Sikora branded the scheme "bizarre".
"It's a very strange rule. Nobody's going on holiday but there will be a few people who will test out the system," he said.
"Britain has put quarantine in far too late. It's ridiculous. If you're going to do it, it should have been done four weeks ago, not now. This is just silly. It's just tokenism.
"It's unenforceable. Nobody's going to be travelling if they don't have to at the moment. People aren't looking to go on holiday, but if they do, they'll try and go by Dublin."
He also added that he believed the steps had been taken for political rather than scientific reasons by the Government.
However, the scheme has been defended by First Minister Arlene Foster, who insisted the new rules were necessary.
Speaking at Monday's daily Covid-19 Stormont briefing, she said: "I certainly don't think that it's a waste of time, because obviously if people are coming in from places where the coronavirus infection rate is higher, then we run the risk of carrying the virus back in again to the United Kingdom.
"That's certainly something we don't want to see happening. We want to eradicate it from Northern Ireland."
Mrs Foster continued: "That's what we're focusing on doing ... We'll have to work with the UK Borders Agency to ensure that it is operable when visitors come. At the moment we have very few visitors, but obviously that will rise again as the lockdown restrictions are lifted."
However, Deputy First Minister Michelle O'Neill acknowledged during the briefing that the scheme's complexities pose problems for the PSNI.
"We looked very carefully at the level of fines that will be associated with not complying," she said. "No doubt it's difficult for the PSNI, across many of the regulations, to enforce it, but we continue to work with them to ensure that people comply with the regulations as drafted."
Guidance released by the Department of Health here continues to advise that travel to other parts of the UK and Irish Republic "should only be undertaken if necessary".
"You are strongly advised not to book foreign travel or travel abroad unless it is essential," said a spokesperson.