"he proceeded to tell me about a “plan” he had come up with to ensure he would be accepted by a good graduate school. He told me that two of his four grandparents were descended from Sephardic Jews who’d fled Spain in the 1500s. This, he said, made him “technically, part Hispanic”—and thus eligible for preferential admission to graduate-school programs. I tried to discourage Daniel from putting this plan into action. I told him I thought it was deceptive and dishonest."

But how do they determine ethnicity when it comes to affirmative action?

Just subjective self-identity?

Visually? I.e "measuring skulls and skin colors"?

Ask your peers what they think you are and base it on that?

Need at least N generations of ancestry to some specific place?

N % DNA match common to some specific group of genes?