The Law: Downgrading Citizens

If an American marries a foreigner and lives abroad permanently—as roughly 200,000 Americans do—are his or her children U.S. citizens?

The answer depends largely on the whim of Congress. At first, the law required that the child's father be a U.S. citizen who at one time had resided in the U.S. Later, either parent's residency sufficed, but the children were required to live in the U.S. for a specific period of time to maintain their citizenship.

In 1967 the Supreme Court ruled that Congress had no power to strip a person of citizenship: he had...