26 U.S.C. § 5386

Special natural wines are the products made, pursuant to a formula approved under this section, from a base of natural wine (including heavy-bodied blending wine) exclusively, with the addition, before, during or after fermentation, of natural herbs, spices, fruit juices, aromatics, essences, and other natural flavorings in such quantities or proportions as to enable such products to be distinguished from any natural wine not so treated, and with or without carbon dioxide naturally or artificially added, and with or without the addition, separately or in combination, of pure dry sugar or a solution of pure dry sugar and water, or caramel. No added wine spirits or alcohol or other spirits shall be used in any wine under this section except as may be contained in the natural wine (including heavy-bodied blending wine) used as a base or except as may be necessary in the production of approved essences or similar approved flavorings. The Brix degree of any solution of pure dry sugar and water used may be limited by regulations prescribed by the Secretary in accordance with good commercial practice.

Special natural wines may be cellar treated under the provisions of section 5382(a) and (c).