27 CFR 25.181: Eligibility.

A brewer may remove beer without payment of tax for transfer to any other brewery of the same ownership. These removals include a removal from a brewery owned by one corporation to a brewery owned by another corporation if (a) one corporation owns the controlling interest in the other corporation, or (b) the controlling interest in each corporation is owned by the same person. Beer removed under this section may, while in transit, be reconsigned to another brewery of the same ownership or be returned to the shipping brewery.