My Dual Citizenship Is None of Bernie Moreno’s Business

Such a vibes-based policy would cause very real harm to millions of Americans and to the U.S. itself. To understand how, it’s helpful to have some knowledge of how nationality laws work.

There are two main principles that form the basis of nationality laws worldwide: jus soli, or law of the soil, and jus sanguinis, or law of the blood. Derived from English common law and prevalent in most countries in the Americas, including the U.S., jus soli is what Americans often call “birthright citizenship” and means that one acquires a country’s citizenship through birth on its sovereign soil. Jus sanguinis comes from the Napoleonic Code and is the basis of nationality laws in most of Europe, the Middle East, and Asia. It confers citizenship at birth via one or both parents, often irrespective of birthplace.

The nationality laws of most jus soli countries, including the U.S., have elements of jus sanguinis, such as granting citizenship to children of citizens born abroad. At the same time, jus sanguinis countries’ laws often result in children born in jus soli countries acquiring dual citizenship at birth. And many jus sanguinis countries—particularly in Europe—consider certain descendants of emigrants to be citizens, meaning that many Americans may unknowingly already have European citizenship or at least the eligibility for it.