The Zoning Regulations exclude fences from yard setback requirements under Section B-324.1(b): 

A fence or retaining wall constructed in accordance with the Construction Code may occupy any yard required under the provisions of this title; and. . .  

The Zoning Administrator has determined that the Zoning Regulations do not regulate fences for lot occupancy purposes as well. However, no fence may be erected so as to block a driveway or other means of access to a required parking space, under Section C-711.3: 

All required parking spaces, other than as permitted in Subtitle C § 711.4, shall be accessible at all times from a driveway accessing either:  

(a) An improved street, except as restricted in Subtitle C § 711.9; or  

(b) An improved alley or alley system with a minimum width of ten feet (10 ft.). 

Therefore, although the Office of Zoning Administration does not generally review applications for fences, the placement of a fence that could block access to a driveway or to a parking space, would be subject to review and denial, by the Office of Zoning Administration.  Fences are separate and distinct from Retaining Walls which are addressed in Subtitle C § Chapter 14.