The two Italian marines have not been charged over the fishermen's deaths but were barred from leaving India.
The Italian government on Tuesday said India's jurisdiction over two Italian marines accused of killing two Indian fishermen in 2012 during an anti-piracy mission is "suspended".
"Italy considers India's jurisdiction over the case to be suspended and therefore legally overridden," the Italian foreign ministry said in a statement.
The statement came after the Indian Supreme Court ruled on Tuesday that one of the marines, Massimiliano Latorre, could stay in Italy until September 30 for medical treatment.
Italy took the case to international arbitration last June and the Hamburg-based International Tribunal for the Law of the Sea ruled in August that India had no jurisdiction in the case, referring it to the International Court of Justice in The Hague.
Mr Latorre has been in Italy for the past 18 months, where he had heart surgery after suffering a stroke.
Italy said on Tuesday it has also requested that the second marine, Salvatore Girone, return to Italy and stay in his homeland until the arbitration verdict in the case, which is expected in August 2018.
Mr Girone and Mr Latorre have not been charged over the fishermen's deaths but were barred from leaving India and ordered to stay at the Italian ambassador's residence and report regularly to police.
The Hague tribunal is expected make a decision on Mr Girone in the next few days, the Italian foreign ministry said.
Last week, Italian President Sergio Mattarella voiced solidarity with Mr Girone and Mr Latorre, saying the legal wrangle was "dragging on too long".
The shooting dead in February 2012 of the two fisherman by Mr Latorre and Mr Girone as they guarded an Italian oil tanker off India's southern state of Kerala sparked a diplomatic incident and the case has strained relations between the two countries.
Mr Latorre and Mr Girone allege they believed the unarmed fishermen were pirates.
Rome claims the marines are immune to prosecution since they were serving on a United Nations-backed anti-piracy mission and the oil tanker they were guarding was in international waters at the time of the incident.