D.C. Mun. Regs. tit. 4, r. 4-804
No employer, housing provider, public accommodation, educational institution, or any agency of the District of Columbia government or its contractors shall require individuals to dress or groom themselves in a manner inconsistent with their sex or their gender identity or expression.
Employers, housing providers, public accommodations, educational institutions, and agencies of the District of Columbia government and its contractors may prescribe standards of dress which shall serve a reasonable business purpose, as long as such standards do not discriminate or have a discriminatory impact on the basis of an individual's sex or the individual's gender identity or expression.
Except as otherwise provided in this chapter, the Office and Commission adopt and incorporate by reference the provisions of 4 DCMR § 512 (1995).
D.C. Mun. Regs. tit. 4, r. 4-804