DC code is not applicable. It's National Park Service regulations that govern most of the monuments around here. Or, as I mentioned, in the case of certain facilities such as the National Arboretum or the National Forests, the Department of Agriculture regulates. Each location seems to have their own fee schedule and set of rules.
Originally Posted by Lopaka
The rent-a-cops at the Arboretum, as well as the clone at the information desk who will hand you the rules permitting non-commercial photography will both then tell you that the tripod you are carrying requires a permit. The permit fee is $500/day. No amount of cajoling on your part will penetrate the thick skull plate of these creatures to whom 2+2=4 and tripod=commercial photographer.