When catching spies, it is tempting to cast a broad net despite risk of making false accusations. Recently, the Justice Department has done just that. In an effort to crack down on what it depicts as an intellectual espionage campaign by China, it has revved up its prosecutions for scientific espionage and intellectual property theft against Asian-American citizens—from the notable case of Wen Ho Lee at the Los Alamos National Laboratory in 1999, to Gang Chen at MIT this January. It’s a familiar cycle, yet somehow shocking each time: immigrant and naturalized scientists are accused of disloyalty. Many are preemptively...