Scholars have often used generational changes in citizenship norms to theorize new forms of youth political expression on social media. Public opinion data has been employed to demonstrate that young people’s perceptions of what it means to be a “good citizen” (i.e., injunctive citizenship norms) have shifted toward models of citizenship that value self-expression. Yet several fundamental assumptions of this dominant image of the young “expressive citizen” remain untested. Using data from a national survey of young Americans (ages 18–24) collected during the 2018 US midterm election, the present study examines: a) if youth indeed view expression as a relatively important part of being a good citizen; and b) if injunctive norms concerning political expression are positively associated with engagement in political expression on social media. Findings indicate that injunctive expressive norms are distinct, but rated as the least important of all injunctive norms. Further, injunctive expressive norms were only modestly associated with social media political expression and difficult to empirically distinguish from what respondents viewed as personally important (i.e., personal expressive norms). While these findings challenge the way past research has theorized and measured the normative role of political expression among young people, they also reveal promising future directions. Specifically, the finding that traditionally marginalized youth place more normative value on political self-expression suggests an important next step for studying the expressive citizen in the age of social media.