D.C. Mun. Regs. tit. 4, r. 4-506
An employee is entitled to equal treatment in all those aspects of employment protected under Title I of the Act. The following are examples of terms, conditions, rights, and privileges:
A discriminatory practice shall include, but is not limited to, any practice or policy used by an employer to distinguish, set apart, or show a difference in treatment or which operates to the disadvantage of a protected group without a valid business necessity.
It shall be a discriminatory practice to require employees to use only the English language while on the employer's premises.
It shall be viewed as a discriminatory practice to allow employees of one class to be addressed only by the titles of "Mr.," "Mrs.," "Miss," or "Ms." while allowing employees of another class to be addressed by their first names.
An employer shall be responsible for the discriminatory actions of its supervisory personnel. An employer shall also be responsible for the discriminatory actions of its other employees of which it knew or should have known.
Codes for dress and appearance shall be applied equally to all employees performing the same kind of work. Any restriction or limitation on dress or appearance shall be a result of a reasonable business purpose. In the absence of a reasonable business purpose, an employer shall not refuse to allow an employee to wear a hair or dress style symbolic of national origin, religion, or race.
All facilities shall be available to all employees on a non-discriminatory basis. This includes lunchrooms, snackbars, recreation areas, and off-site facilities provided by an employer, such as employee social clubs, health clubs, swimming pools, etc. Locker rooms, restrooms, and shower rooms may be lawfully segregated based on sex.
It shall be a discriminatory practice for an employer to seek to evade responsibility for discrimination by transferring the use or control of facilities to employees or employee groups.
It shall be the responsibility of the employer to use all reasonable means to assure the full and equal participation of a member of a protected class in a work unit in which members of that protected class were not previously employed.
Employers shall secure all personnel files and other documents which contain information which is susceptible to use for a discriminatory purpose and shall allow access to the files only on a "need to know" basis.
Post-hiring inquiries shall not be used for discriminatory purposes.
D.C. Mun. Regs. tit. 4, r. 4-506