The United Arab Emirates was ordered by the highest UN court on Monday to immediately allow Qatari families affected by a dispute between the countries to reunite, imposing the measure before it hears the full case filed by Qatar at a later date.
The UAE had argued before judges at the International Court of Justice (ICJ) in The Hague on June 28 that the case was without merit and should be dismissed, but on Monday the judges granted Qatar's request for so-called provisional measures by a majority vote of 8 to 7.
The UAE, Saudi Arabia, Bahrain and Egypt imposed a boycott on Qatar in June 2017, severing diplomatic and transport ties and accusing it of supporting terrorism, which it denies.
According to Qatar, which filed the suit in June, the UAE has as part of the boycott expelled thousands of Qataris, blocked transport and closed down the offices of the Doha-based Al-Jazeera news channel.
"Many Qataris residing in the UAE appeared to have been forced to leave their place of residence without the possibility of return," the judges' ruling said.
"There is an imminent risk that the measures adopted by the UAE could lead to irreparable prejudice to the rights invoked by Qatar."
Qatar's foreign ministry spokeswoman Lulwa al-Khater, welcomed the ruling.
"This is only the first step on a long road to defend our rights, but at the same time this sends an early strong signal that there will be no tolerance shown to countries that take arbitrary measures against Qataris," she said in Arabic language comments published by state news agency QNA.
The United Arab Emirates said it was already implementing the provisional procedures ordered by the court.
"The judges rejected the Qatari demands and called for three procedures relating to families, students and adjudication and they are measures the UAE has already implemented according to its national regulations," UAE Minister of State for Foreign Affairs Anwar Gargash said in a Twitter post in Arabic.
The court found that mixed UAE-Qatari families have been separated, Qatari students have been deprived of the opportunity to complete their education, and Qataris have been denied equal access to justice.
"The court concludes that the conditions required by its statute for it to indicate provisional measures are met," it said.
The ICJ is the United Nations venue for legal disputes between states. Its verdicts are binding, but it has no enforcement powers.
Final verdicts generally take years and no date was set for the case to be heard in full.