The world is outraged at Israel's blockade of Gaza. Turkey denounces its illegality, inhumanity, barbarity, etc. The usual U.N. suspects, Third World and European, join in. The Obama administration dithers.

But as Leslie Gelb, former president of the Council on Foreign Relations, writes, the blockade is not just perfectly rational, it is perfectly legal. Gaza under Hamas is a self-declared enemy of Israel — a declaration backed up by more than 4,000 rockets fired at Israeli civilian territory. Yet having pledged itself to unceasing belligerency, Hamas claims victimhood when Israel imposes a blockade to prevent Hamas from arming itself with still more rockets.

In World War II, with full international legality, the United States blockaded Germany and Japan. And during the October 1962 missile crisis, we blockaded ("quarantined") Cuba. Yet Israel is accused of international criminality for doing precisely what John Kennedy did: impose a naval blockade to prevent a hostile state from acquiring lethal weaponry.

Oh, but weren't the Gaza-bound ships on a mission of humanitarian relief? No. Otherwise they would have accepted Israel's offer to bring their supplies to an Israeli port, be inspected for military materiel and have the rest trucked by Israel into Gaza — as every week 10,000 tons of food, medicine and other humanitarian supplies are sent by Israel to Gaza.

Why was the offer refused? Because, as organizer Greta Berlin admitted, the flotilla was not about humanitarian relief but about breaking the blockade, i.e., ending Israel's inspection regime, which would mean unlimited shipping into Gaza and thus the unlimited arming of Hamas.

Israel has already twice intercepted weapons-laden ships from Iran destined for Hezbollah and Gaza. What country would allow that?

But even more important, why did Israel even have to resort to blockade? Because, blockade is Israel's fallback as the world systematically delegitimizes its traditional ways of defending itself — forward and active defense.

• Forward defense: As a small, densely populated country surrounded by hostile states, Israel had, for its first half-century, adopted forward defense — fighting wars on enemy territory (such as the Sinai and Golan Heights) rather than its own.

Where possible (Sinai, for example) Israel has traded territory for peace. But where peace offers were refused, Israel retained the territory as a protective buffer zone. Thus Israel retained a small strip of southern Lebanon to protect the villages of northern Israel. And it took many losses in Gaza, rather than expose Israeli border towns to Palestinian terror attacks.

But under overwhelming outside pressure, Israel gave it up. The Israelis were told the occupations were not just illegal but at the root of the anti-Israel insurgencies — and therefore withdrawal, by removing the cause, would bring peace.

Land for peace. Remember? Well, during the past decade, Israel gave the land — evacuating South Lebanon in 2000 and Gaza in 2005. What did it get? An intensification of belligerency, heavy militarization of the enemy side, multiple kidnappings, cross-border attacks and, from Gaza, years of unrelenting rocket attack.

• Active defense: Israel then had to switch to active defense — military action to disrupt, dismantle and defeat (to borrow President Obama' s description of our campaign against the Taliban and al-Qaeda) the newly armed terrorist mini-states established in southern Lebanon and Gaza after Israel withdrew.

The result? The Lebanon war of 2006 and Gaza operation of 2008-09. They were met with yet another avalanche of opprobrium and calumny by the same international community that had demanded the land-for-peace Israeli withdrawals in the first place. Worse, the U.N. Goldstone report, which essentially criminalized Israel's defensive operation in Gaza while whitewashing the casus belli — the preceding and unprovoked Hamas rocket war — effectively delegitimized any active Israeli defense against its self-declared terror enemies.

• Passive defense: Without forward or active defense, Israel is left with but the most passive and benign of all defenses — a blockade to simply prevent enemy rearmament. Yet, as we speak, this too is headed for international delegitimation.

But, if none of these are permissible, what's left?

Nothing. The whole point of this relentless international campaign is to deprive Israel of any legitimate form of self-defense.

The world is tired of these troublesome Jews, six million — that number again — hard by the Mediterranean, refusing every invitation to national suicide. For which they are relentlessly demonized, ghettoized and constrained from defending themselves, even as the more committed anti-Zionists — Iranian in particular — openly prepare a more final solution.