26 U.S.C. § 5365

The Secretary may require by regulations such segregation of operations within the premises, by partitions or otherwise, as may be necessary to prevent jeopardy to the revenue, to prevent confusion between untaxpaid wine operations and such other operations as are authorized in this subchapter, to prevent substitution with respect to the several methods of producing effervescent wines, and to prevent the commingling of standard wines with other than standard wines.