The U.S. Supreme Court issued a 5-4 decision this morning, knocking down a vague provision in immigration law, making it harder to deport immigrants convicted of certain crimes.

The case Sessions v. Dimaya does not change deportation decisions for obviously violent crimes like rape or murder, but the general label for “crime of violence” is too vague for courts to interpret, not allowing, as Justice Elena Kagan wrote, “ordinary people” to have “fair notice'’ of what is proscribed by the law.

Evelyn Cruz, clinical professor of law at Arizona State University, explains what this means.