People arriving in Northern Ireland from Spain will now need to qurantine for 14 days.
It follows a recent surge of new coronavirus cases in the country.
The North's health minister, Robin Swann, says it's a "cause for concern" and that he spoke with his UK counterparts before taking the decision.
British tourists flying home from Spain have reacted angrily to the decision to take the country off the safe-travel list.
There's also criticism of the timing of the announcement on a weekend, meaning many travelers will be unable to contact their travel agents straight away.
The re-imposition of quarantine rules applies to all arrivals into the UK from Spain.
British Foreign Secretary Dominic Raab says the measure is a necessary one:
