After a U.S. navy ship fired shots at a small boat, killing one Indian fisherman and injuring three others, the U.S. expressed its condolences.

But the U.S., in a note from the embassy in New Delhi, also defended the decision to fire, saying “the vessel disregarded non lethal warnings and rapidly approached the U.S. ship. They said they shot after theses warnings were ignored.

Some of the fishermen who were on board the small boat have challenged this claim. Speaking to reporters on Tuesday, one of the fishermen said the U.S. navy ship started shooting “without any warning.

A similar thing happened in February, when Italian marines on board of a commercial ship shot at a fishing boat off the coast of Kerala state. Two fishermen, who the marines mistook for pirates, were killed.

At the time, Italian officials said that, before shooting, the naval officers, who were later detained, flashed lights and followed other procedures to deter the boat from getting closer. They say they fired into the air and water after the boat failed to change its course.

In both cases naval officers say they gave plenty non-lethal warnings before firing. In both cases the warnings were ignored. In both cases there were casualties.

This raises the question of whether it’s fair to assume fishermen can understand these warning signs. The episodes mentioned above suggest it’s not.

The main problem is that there is no uniform code of conduct at sea – and if there are no set rules, you can’t really expect people to follow them, say experts in international maritime law.

They point out that warning signs differ from port to port, from vessel to vessel and country to country.

Medium-to-large vessel typically issue warnings through a marine high frequency radio. In most cases, this is what prevents potential conflicts at sea, says Noel Choong, who heads the piracy division at the International Maritime Bureau, a Kuala Lumpur-based non-profit group.

Small vessels might not even be equipped with such facilities, allowing more room for sea incidents to escalate, says Mr. Choong. Moreover, many local fishermen, even if they have the radio, may lack the linguistic skills to effectively communicate with foreign vessels cautioning them to stay away.

From the point of view of the vessel that fears an attack, this makes it “undoubtedly difficult to differentiate between local fishermen and pirates, says Mr. Choong.

If verbal communication fails, ships typically send visual warnings, he adds. These can range from flashing lights on the approaching vessel to firing a round of bullets in the air or water.

The rationale behind this, he says, is that most people who see these warnings would use common sense and get out of the way.

Some maritime experts, however, note there are many grey areas.

“How close is too close? wonders Uday Bhaskar, a retired senior Indian navy official. “And who defines it?

For instance, he says that local fishermen may consider 50 meters a safe enough distance to maintain between vessels, even if they notice visual warnings. But a larger, state-run ship, may consider a vessel that is 100 meters or 200 meters away as a possible threat and consider opening fire on it. (The U.S. military said naval officers opened fire on the small boat in the Persian Gulf when it was 90 meters away.)

“There are no set guidelines for these mechanisms, says Mr. Bhaskar, who is also a former director at the National Maritime Foundation, a state-run body that focuses on maritime security.

“Unless there are uniform rules of engagement widely accepted as protocol by all ship owners, such incidents cannot be prevented, he adds.

Mr. Bhaskar said there is an urgent need to “recognize, recommend and rectify such loopholes in the existing maritime framework.

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