A child born to an American is an American citizen -- right? Not exactly. Everyone born in the U.S., of course, gets citizenship, much to Donald Trump's chagrin. Children of American citizens born abroad get "derivative citizenship," or citizenship through parents, only under certain conditions.
When it comes to derivative citizenship, the deciding factor is often the American parent's gender, if the child was born out of wedlock. That means many children born outside the U.S. to an American father, for example, are denied citizenship that would be available had they been born to an American woman. An older version of that system is unconstitutional, a recent Second Circuit decision declared in an opinion that might put current immigration laws at risk.