The death of a suspected pirate off the coast of Somalia has drawn attention to the use of armed private security contractors on board merchant vessels.
The incident, which involved guards aboard the Panamanian-flagged MV Almezaan, is believed to be the first of its kind.
But several organisations, including the International Maritime Bureau (IMB), have previously expressed concerns over the use of armed security contractors.
"While we understand that owners want to protect their ships, we don't agree in principle with putting armed security on ships," IMB director Capt Pottengal Mukundan told the BBC News website.
"Ships are not an ideal place for a gun battle."
One argument is that the use of armed operatives could encourage pirates to use more violence when taking a ship.
But Mr Mukundan said he had seen no evidence that there had been much of an increase in the use of armed guards by merchant ship owners.
Dozens of warships patrol the waters off the Somali coast, but this has not deterred the pirates. The amount of ocean to patrol is extremely vast and pirates have responded to the increased naval presence by moving attacks farther out to sea.
"The naval forces are displacing the threat - they can't be everywhere at once," says Nick Davis, chief executive of Merchant Maritime Warfare Centre, a not-for-profit organisation.
"Almost the whole of the Indian Ocean region - some 5 million square nautical miles - is a security risk."
But the shipping industry has, so far, largely resisted arming their boats - not least because this would deny them port in some nations. Furthermore, arming the ships can raise liability issues and increase insurance costs.
Christopher Ledger, director of security firm Idarat Maritime, says the use of private operatives is not necessary and that ship owners can find other ways to protect themselves, such as boosting training, carrying out more drills and purchasing equipment that could prevent pirates boarding a vessel.
"Private security guards are not necessary, they simply muddy the water," he said. "They are often foreign to the crew themselves and they don't know the ship well.
"Many are former soldiers that have been in Iraq or Afghanistan and they think they can shake the dust off their shoes and make it as a private security guard. Their day rate is pretty high and the crew have to find ways to get them on and off the vessels."
Their presence, he said, would only lead to "more spilt blood".
This month, international shipping law firm Ince and Co released a report highlighting the issues arising from the use of armed guards. It pointed out that a fundamental question arose as to who would authorise the use of force.
Stephen Askins, a lawyer with Ince, told the BBC News website that the debate on the use of armed guards was one that polarised the industry.
"Most industry bodies and ship-owners are against them," he said. "But no ship with an armed guard has been hijacked, so there are those - particularly those who have had hijacked ships - who think they are necessary."
He said private security companies had come into their own in places like Iraq and had seen seen the maritime sector as potentially lucrative.
"Many have moved across but there is no system of accreditation, so there is no way of knowing the good from the bad," he said.
Most security operatives are former British servicemen, but there are also operatives from the US, Australia, New Zealand and South Africa.
Mr Askins said some firms provided armed escort vessels, but that these did not have any status in international law.
"The various conventions dealing with piracy relate to states and their navies," he said. "The rights that they are given, like the right of innocent passage relate to military ships. There are also issues over the use of armed force. The relevant law is the law of the flag state, but a merchant ship could, for example, be Panamanian and the escort ship could be, say, UK flagged."
But he also pointed out that there were some very good companies that had "robust rules of engagement".
"Lethal force for them would come after a series of steps including warning shots. The good companies would follow that procedure. Normally that would be enough to deter an attack."
In May 2009, the US Coast Guard drafted a maritime security directive that would require US-flagged ships sailing around the Horn of Africa to post guards, and ship owners to submit anti-piracy security plans for approval.
At the time, the Coast Guard's director of prevention policy, Rear Admiral James Watson, said that they expected to see "additional security" that could "involve the use of firearms".
He added that they were "looking for things that work but that don't make the situation worse".
The directive has not yet passed into law.
For now, the handling of Tuesday's shooting by a private security operative will be watched closely by legal experts.
An independent inquiry is planned, but first investigators will need to establish who had jurisdiction - the flag the vessel was flying, its owners or the nationality of the contractors - and who was responsible for the security contractors.