All of a sudden, everyone in the United States wants to know if Ted Cruz – who was born in Calgary to an American mother – is eligible to be our president. But I have a different question: Why do you have to be a natural-born citizen in order to lead the country?

In Canada, you don’t; that’s why the British-born John Turner could serve as prime minister in 1984. Why do Americans think the president has to be American from birth?

For our Founding Fathers, the answer lay in national security. If foreign-born Americans could become president, foreign powers might use them to undermine the new republic. Just 15 years before our Constitution was drafted, three countries – Austria, Prussia and Russia – conspired to elect a puppet king in Poland; shortly after that, the three powers partitioned Poland among themselves. Unless we barred foreign-born candidates from our presidency, warned one delegate to the Constitutional Convention, “the fate of Poland may be that of united America.”

In 1787, these fears made sense. Today, our round-the-clock media scrutiny would quickly expose any foreign-born candidate who was serving as a foreign agent. Indeed, a hostile country wishing to infiltrate the White House would be much wiser to work through a native-born politician, who would naturally draw less attention than a foreign-born one.

Unlike the framers of the Constitution, moreover, we live in a multicultural democracy. They could not imagine someone like Barack Obama becoming president, because they restricted the full rights of citizenship to white men. ...