The Supreme Court ruled on Friday that one of the Italian marines detained for the 2012 killing of two fishermen can go home for medical treatment.
The court said it had agreed to allow Massimiliano Latorre to spend four months at home after the Italian ambassador undertook to ensure that he returned to India to stand trial.
"In the face of no objection from union of India, we let the marine travel to Italy," said Chief Justice RM Lodha
Latorre wants to return to Italy to recuperate after he was hospitalised in New Delhi with ischaemia -- a restricted blood supply that can lead to a stroke.
The court asked Latorre to give an unequivocal and unambiguous undertaking about his date of departure and arrival back in India.
The 47-year-old was discharged from hospital on Sunday and is not thought to be in any immediate danger, but Italy's foreign minister Federica Mogherini insisted that his chances of a full recovery would be increased by being allowed home.
Latorre and fellow marine Salvatore Girone are accused of shooting the fishermen while serving as part of an anti-piracy mission on an Italian-flagged oil tanker, the Enrica Lexie, off the coast of Kerala.
The Italian sailors say they mistook the fishing boat for a pirate vessel and fired what were intended to be warning shots.They have been living at Italy's embassy pending a possible trial and were not allowed to leave India.
Italy says the pair should be tried on home soil since the shootings involved an Italian-flagged vessel in what Rome insists were international waters.
India, however, asserts the killings took place in waters under its jurisdiction.