Gender policing is the imposition or enforcement of normative gender expressions on an individual who is perceived as not adequately performing, through appearance or behavior, the sex that was assigned to them at birth (see gender performativity). Gender policing serves to devalue or delegitimize expressions that deviate from normative conceptions of gender, thus reinforcing the gender binary. According to Judith Butler, rejection of individuals who are non-normatively gendered is a component of creating one’s own gender identity. Gender mainstreaming is a public policy concept, whereas gender policing is a more general social phenomenon.