By Dan Williams and Jonathan Saul
JERUSALEM/LONDON (Reuters) - Anticipating fresh bids by pro-Palestinian activists to sail against its Gaza Strip blockade, and hoping to avoid a repeat of its bloody boarding of a Turkish aid ship in May, Israel has turned to maritime law.
Israeli officials say vessels will be warned in advance that they face costly impoundment and the possible detainment of crews -- a strategy first floated in July when the threat of such action helped turn a Libyan-chartered ship away from Gaza.
"The legal approach proved effective as a deterrent, and we're prepared to see it through as a punishment," said one senior government official, declining to be named.
"If we are to pay a price for defending the blockade, the other side will pay a price for challenging it."
Israel triggered world outcry in May after its forces killed 9 Turks in brawls aboard the Mavi Marmara, a converted cruise liner that tried to lead an aid flotilla to impoverished Gaza, whose 1.5 million Palestinians are ruled by Hamas Islamists.
Israel says its blockade is needed to prevent weapons from reaching Hamas, which refuses to recognise Israel.
Maritime specialists say international law allows a sovereign nation to seize a vessel that runs a declared blockade. That could discourage firms renting out ships to pro-Palestinian campaigners but, arguably, less so in cases like the Mavi Marmara, where the activists buy the ship outright.
"Many ship owners will look at the possibility or likelihood that their vessel will be impounded or fined or seized outright," said J. Peter Pham, a strategic adviser to the U.S. and European governments.
"Those are losses for which they are not insured and for which the non-governmental groups are not going to make good on for them."
THREATS AT SEA
In July a charity belonging to one of Libyan leader Muammar Gaddafi's sons chartered the cargo ship Amalthea for a Gaza aid run. Israeli media aired recordings of the navy warning the captain he would be held responsible for any showdown at sea.
According to Israeli and Libyan officials, a dispute ensued aboard the ship over where to dock. The captain and crew prevailed, taking the Amalthea to El Arish in nearby Egypt.
"Israeli authorities, through the navy, threatened legal action against the ship," said Alex Angelopoulos of Greece's ACA Shipping Corp, which owns the Amalthea.
"The threats were taken into consideration, but the decision (to change course) was taken after long talks with the ship's charterers," he said, adding that were the ship impounded it would mean losses of some 5,000 euros ($6,350) a day.
Another Israeli official said permanent confiscation of ships was "out of the question."
"It would simply be untenable both legally and practically. But we can exert pressure by virtue of the fact that a ship owner stands to lose a lot of money for each day of temporary impoundment in Israel, not to mention the long-term cost of the vessel going rusty and neglected," the official said.
The Israelis say they are bracing for possible new Gaza flotillas by groups from Lebanon, Europe and the United States.
Activists might be willing to lose their ships if they thought their actions would bring them global publicity or dent Israeli prestige -- as happened with the May flotilla.
But some shipping experts doubt whether impoundment could be a feasible long-term solution for Israel.
"The real question should be: how long can Israel detain the ship? My guess is not long without positive proof that there was something more than humanitarian aid on board," said John Dalby, chief executive of maritime asset recovery firm MRM.
Daniel Reisner, a former commander of the Israeli military's international law department, said he knew of no legal basis to try foreigners specifically for violating the Gaza blockade.
"In general, the more innocent the cargo, the more this diminishes the chances of a prosecution," he said.
Of the seven ships in the Mavi Marmara flotilla, four remain berthed in Israel after the three Turkish-owned vessels were returned unconditionally as a fence-mending gesture to Ankara.
Israel's Defence Ministry said unspecified "private entities" had sought to reclaim two of the impounded ships but had yet to furnish proof of ownership. The remaining two ships have gone unclaimed while Israel tries to locate their owners.
"It's a double-edged sword: if you have no hope of recovering the actual impound fees then you are stuck with a boat that you neither want nor will be able to get rid of easily," said Pham.
Banner of flotilla stopped in May 
Non-governmental organizations (NGOs) throughout Europe and the United States are currently assembling a flotilla of up to 20 ships, which will set sail for the Gaza strip in the coming months in an attempt break the Israeli blockade of the Palestinian territory. Israeli-Swedish activist Dror Feiler said that the goal of the new flotilla is to double the size of the previous one, and for it to include more than a thousand people. "The Israeli Army can stop 12 to 50 ships if it wants," Feiler said. "Nonetheless there are so many ships since so many people want to get together to stop the siege, which is a collective punishment on the people of Gaza and is unacceptable."

The Israel Defense Force is monitoring the actions of the planned flotilla, according to a report in the '''' on Tuesday. The Israeli army is calling this new fleet of ships "the mother of all flotillas." A wide range of scenarios is being prepared for which include the possibility that due to the larger number of ships reported to be part of the flotilla, the Israeli navy may need to intercept it before the ships get close to Israel's shoreline. Officials say that Israel will warn ship operators that their crew may be detained and the vessel held until impound fees are paid, claiming the backing of international maritime treaties.

"The legal approach proved effective as a deterrent, and we're prepared to see it through as a punishment. If we are to pay a price for defending the blockade, the other side will pay a price for challenging it," a senior Israeli government official. The official declined to be named.

A European campaigner against the blockade, Anwar Ghabi, told Arabic news agency Quds Press that the new flotilla will be backed by hundreds of NGOs, including several human rights groups.

The first flotilla to challenge the blockade was stopped by Israeli naval commandos in May this year. Nine activists were killed, and several dozen activists and seven Israeli commandos were wounded after Israeli troops clashed with activists. Harsh international and domestic criticism followed. Subsequent aid ships were seized or diverted to Egypt.