I support President Donald Trump’s immigration policy. A nation that cannot control its borders cannot sustain democratic self-government, and laws passed by Congress, however flawed, must be enforced if the rule of law is to mean anything. I also support legal immigration, assimilation and the idea that becoming American is a commitment to shared civic norms, not merely a legal status. That is why Immigration and Customs Enforcement officers should not be wearing masks. Masked enforcement — agents conducting arrests with covered faces, no visible names and sometimes no clearly displayed badge numbers — is a mistake. It is not...