Birthright citizenship has been part of the U.S. Constitution for more than 150 years, but why has it become the focus of such intense political debate in recent years? Professor Anna Law breaks down the Supreme Court's decision in Trump v. Barbara, explains what birthright citizenship actually means, and traces the long history of who gets to be an American. Drawing from her new book, she separates fact from fiction on immigration, citizenship, and the Constitution, and explains why understanding that history matters today.

For more on this topic:

• Check out Law's new book, Migration and the Origins of American Citizenship

• Read her blog post, I Read Trump v Barbara So You Don't Have To

• Read her Made by History essay in TIME Magazine, History Shows Why Birthright Citizenship is so Important