D.C. Mun. Regs. tit. 20, r. 20-802
The purchase, sale, offer for sale, storage, transport, or use of coal which contains more than one percent (1%) sulfur by weight in the District shall be prohibited, if the coal is to be burned in the District. However, when the Mayor certifies in writing that the combustion-gas-desulfurization system used at a stationary source results in sulfur oxide emissions no greater than the emissions normally resulting from the burning of coal with one percent (1%) sulfur content, coal of a higher sulfur content may be burned at the stationary source.
Application for a certification shall be made, in writing, to the Mayor by the owner or operator of the stationary source and, upon presentation to a seller of the certification, a copy of which shall be retained by the seller, the sale, purchase, and transportation of the coal shall be permitted.
D.C. Mun. Regs. tit. 20, r. 20-802