The Maltese government has refused to allow a tanker which rescued 102 African migrants to dock in Malta.
It was earlier told by the European Commission that it had a duty to admit the passengers on humanitarian grounds.
The Commission said the EU state had a humanitarian duty to take in the migrants, who were saved from a boat off the Libyan coast.
Among those aboard the tanker are an injured woman, four pregnant women and a five-month-old baby.
But Malta says it told the captain of the tanker - the M/V Salamis - it did not have permission to enter its territorial waters and insists its decision to deny entry is in keeping with international law.
Minister for Home Affairs Manuel Mallia was quoted as saying by the Times of Malta: "There is no doubt that Malta is legally correct... we have documented evidence from the maritime rescue co-ordination centre of Rome."
Maltese naval medics visited the tanker on Tuesday to check the state of health of the migrants and distribute food and water, and the government has now concluded that no evacuations are necessary.
The tiny island state receives thousands of illegal migrants heading to Europe each year.
Hours before the latest incident, 111 mainly African migrants arrived in a rubber dinghy at Delimara, on the south-east coast.
The European Commission had argued that since the ship was now closest to Malta, the island must allow the migrants to disembark as soon as possible.
Any dispute over which country should legally take them should be resolved later, it argued. The immediate concern was to save lives.
The master of the Salamis is credited with saving the migrants' lives. He issued an urgent medical request saying one injured woman needed to be taken immediately to hospital.
But the Maltese medics who visited the tanker on Tuesday found otherwise.
The Liberian-flagged Salamis had been en route from the Libyan port of Khoms, bound for Malta, and was reportedly 24 nautical miles off Malta's coast on Tuesday.
Malta's government says a patrolling Italian navy ship ordered the tanker to take the migrants back to Libya when it was within 50 nautical miles of the Libyan coast.
"The shipmaster ignored guidance from RCC [maritime Rescue Co-ordination Centres] because of commercial interests," Mr Mallia said.
"This is a matter of principle for us, because if we allow this to take place, it will create a dangerous precedent for us. There is no emergency: these people were rescued, they are in a good state, and they were waving at the AFM [Maltese armed forces] helicopter as it descended."
Mr Mallia said he had spoken to the European Commissioner for Home Affairs, Cecilia Malmstroem, who had not been "aware of the entire picture".
On Sunday the Italian navy rescued a group of at least 90 migrants trying to reach Europe from North Africa by boat, and brought them to the island of Lampedusa.
Last month, Maltese Prime Minister Joseph Muscat told EU Council President Herman Van Rompuy that the burden of immigration to the EU should not fall on its smallest member.
While Malta would do its compassionate duty, he added, it would not leave its doors open wide and "welcome boats from Libya and elsewhere as if nothing happened".
"Call us harsh, call us heartless, but we are not pushovers," the Maltese prime minister said.