Tens of thousands of ethnic Armenians fled the region after Azeri forces seized the territory after a lightning offensive.
In a decision on Friday, the International Court of Justice said that previous ethnic Armenian residents must be allowed back and that those who remained there must be kept safe.
“Azerbaijan must … ensure that persons who have left Nagorno-Karabakh after September 19, 2023, and who wish to return to Nagorno-Karabakh are able to do so in a safe, unimpeded and expeditious manner,” presiding judge Joan Donoghue said.
Azerbaijan captured Nagorno-Karabakh, which is internationally recognised as Azeri territory, after defeating separatist ethnic Armenian fighters in a lightning campaign in September. Since the assault, most of the region’s 120,000 ethnic Armenians have fled for neighbouring Armenia.
Yerevan has accused Azerbaijan of ethnic cleansing, while Baku has argued that it is seizing control of a breakaway territory whose status has been contested through several wars.
Azerbaijan’s assault was preceded by a more than nine-month siege that choked off access to essential goods for residents.
The court also stated that Azerbaijan must guarantee that those Armenians who remain in Nagorno-Karabakh “are free from the use of force or intimidation that may cause them to flee”.
Azerbaijan’s foreign ministry said in a statement that it “is committed to upholding the human rights of the Armenian residents of Karabakh on an equal basis with other citizens of Azerbaijan”.
But many ethnic Armenians who fled have expressed doubts that they will be safe if they return to the enclave, if they are allowed back at all, under the rule of what they see as a hostile power.