By underscoring Japan's powerlessness to act or retaliate, the Islamic State group's separate beheading of two Japanese hostages recently has brought Prime Minister Shinzo Abe's cherished goal of reforming the U.S.-drafted Constitution back into national focus. No other country in the world is bound by the kind of constitutional restrictions that were imposed on vanquished Japan by occupying American forces in 1947.

The Constitution prohibits Japan from acquiring the means of war and bars its purely defensive military, called the Self-Defense Forces, from staging rescue missions or other overseas operations to free Japanese hostages. Indeed, to set up wholly defensive armed forces in the 1950s, Japan had to loosely interpret the Constitution's force-renouncing Article 9, which says "land, sea and air forces, as well as other war potential, will never be maintained."

Yet Japan has clung to that Constitution for 68 years without so much as carrying out a single amendment or changing even one word. Many other democracies regard their constitutions not as cast in stone but as open to change so that they stay abreast with new social, technological and economic developments. For example, India — whose constitution is almost as old as Japan's — has incorporated 99 amendments thus far. There have been fewer amendments — 27 — to the U.S. Constitution since its enactment in 1787.