-- With the killing this week of four Americans by Somali pirates, there is renewed debate over how to deal with the piracy problem.

Among those studying the issue is Professor Peter Lehr of the University of St. Andrews in Scotland, author of the book Violence at Sea: Piracy in the Age of Global Terrorism.

Needle in a haystack

Somali piracy has been a tough problem to solve, despite international naval patrols.

?You never have enough warships on station,? Lehr says, ?It?s simply not working.  If you look at the coastline of Somalia alone, that?s 3,300 kilometers we are talking about.  And then take a look at how far away from their own shores they strike.  That?s now 1,500 nautical miles, which means that reaches up to the west coast of India to the Mozambique Channel.  Looking for them is like looking for a needle in a haystack.?

There are two approaches to tackling piracy: by sea and by land, Lehr says.

?The ships on voyage ? freighters, container ships, tankers and yachts, whatever ? they need to have protective measures on their own.  Now again, there are two different approaches.  One is non-violent measures like having razor wire, high pressure hoses if you have a big ship, a 24/7 watch, evasive maneuvers.  And there are now also violent approaches,? he says.

This includes the use of armed security guards on board the vessels.  Pirates getting more violent

Besides the four Americans who were killed after being taken from their yacht, Lehr says a sailor aboard a hijacked vessel was recently shot dead.  ?So the risk to your life as a sailor is now getting higher and higher.  So, although I do not necessarily talk in favor of armed guards on board, that may make sense on certain ships,? he says.

As for the second anti-piracy approach, Lehr says, ?Piracy is a land-based problem, which means in the end you will have to tackle where it comes from and that?s the Somali shores.?

Some analysis say attacking pirate bases on the Somali mainland would violate the country?s sovereignty.

?It is, of course, a problem, not that I?m a specialist in international law.  But one thing you have to note is that Somalia is a failed state.  I think a U.N. decision that would allow us, whoever that is, to get ashore.  We?ve done it already in the early 1990s, as you remember, Operation Restore Hope.?

However, the U.S. effort to break a famine in Somalia eventually led to involvement in Somalia?s political turmoil. ?Which also means that if we, whoever that is, attack pirate lairs on the shore, we might get in conflict with al Shabab,? the Islamist militant group trying to topple the Transitional Federal Government.

He says is al Shabab is eager to take on the ?western crusaders, as they call us.  That might actually worsen the problem.?

Arrest and prosecute

A number of captured pirates have been brought to trial.  But Lehr says that?s not much of a deterrent to attacking ships.

?There?s this joke about catch and release.  Lots of pirates get actually taken on board warships and then put back on their shores without any further ado because many countries are reluctant to actually bring them to justice,? he says.

One example of where it may have worked, he says, is the more than 30-year sentence given to a Somali pirate who was tried in New York for the 2009 hijacking of the Maersk Alabama.

But going to jail in a developed nation may have a certain appeal to a Somali pirate, such as TV and three meals a day.

?So far, even ending up in a prison cell was a kind of a second prize for the pirate.  Either you get rich (from ransom) or at least you get a decent life.  If you take a look at the grim situation over there in Somalia, they do everything to escape from that,? says Lehr.

Saudi Arabia

He says getting a U.N. mandate to allow the international community to attack pirate bases is only part of the solution.

He says, ?There are some powerful navies in the region, who are doing actually nothing.  I would point out Saudi Arabia, for example, which has quite a sophisticated navy and quite a lot of money.  Some Saudi tankers were already taken hostage by pirates, so why are they not contributing to anti-piracy operations as they should

Saudi involvement, he says, would dispel any image of a western crusade against a Muslim state.