The Citizenship Clause, ratified in 1868 after the Civil War, was included to ensure that formerly enslaved people would be citizens. It effectively overturned the notorious Dred Scott decision, in which the Supreme Court held that Black people, no matter their status, were not citizens.

The U.S. Supreme Court is poised on Thursday to consider Donald Trump's attempt to broadly enforce his executive order to limit birthright citizenship, a move that would affect thousands of babies born each year as the Republican president seeks a major shift in how the U.