Does support for tough policies against undocumented immigration reflect anti-immigrant sentiments or a neutral concern about upholding laws? This study addresses the question by examining the relationship between different expressions of national identification and ethnocentric enforcement bias—that is, support for punishment of law-breaking immigrants but not law-breaking American employers who knowingly hire undocumented immigrants. Results revealed an association of this enforcement bias with nationalism (an ethnocentric engagement with national identity) but not with patriotism (a more critical engagement with national identity). A moderation analysis indicated that the relationship between nationalism and ethnocentric enforcement bias was most evident among participants who endorsed a “culture”-based construction of American identity in terms of American citizenship and ability to speak English. Discussion focuses on policy developments that reflect a symbolic threat to culture-based constructions of American identity and on the implications for fair and just enforcement of immigration policy.