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 declared enemy of Israel - a declaration backed up by more than 4,000 rockets fired at Israeli territory. Yet, having pledged itself to unceasing belligerency, Hamas claims victimhood when Israel imposes a blockade to prevent it from arming with 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 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. Or they would have accepted Israel's offer and taken their supplies to an Israeli port to be inspected for military matériel and then trucked into Gaza - as, every week, 10,000 tons of food, medicine, and 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 have to resort to a blockade? Because a blockade is Israel's fallback as the world systematically delegitimizes its ways of defending itself.

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 traded territory for peace. But where peace offers were refused, it retained territory as a buffer. 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 terrorist 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 anti-Israel insurgencies - and therefore withdrawal would bring peace.

Land for peace. Remember? Well, Israel gave the land - evacuating southern 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 triggered yet another avalanche of opprobrium and calumny by the same international community that had demanded the land-for-peace Israeli withdrawals. 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 terrorist enemies.

Passive defense: Without forward or active defense, Israel is left with 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 delegitimization.

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

Nothing. The whole point of this relentless international campaign is to deprive Israel of any legitimate 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 demonized, ghettoized, and constrained from defending themselves, even as the more committed anti-Zionists - Iranian in particular - openly prepare a more final solution.

Charles Krauthammer is a Washington Post columnist.

He can be reached at letters@charleskrauthammer.com.