I'm no expert at TTB rules and regs, but doesn't TTB Rule 5.36(d) already cover this for most whiskies (with a a few exceptions)? Chuck Cowdery was making a lot of noise about this a few years back. I think a couple of MGP/LDI customers ran afoul of it and made some news.
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§ 5.36 Name and address.
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(d) State of distillation. Except in the case of “light whisky”, “blended light whisky”, “blended whisky”, “a blend of straight whiskies”, or “spirit whisky”, the State of distillation shall be shown on the label of any whisky produced in the United States if the whisky is not distilled in the State given in the address on the brand label. The appropriate TTB officer may, however, require the State of distillation to be shown on the label or he may permit such other labeling as may be necessary to negate any misleading or deceptive impression which might be created as to the actual State of distillation. In the case of “light whisky”, as defined in § 5.22((3), the State of distillation shall not appear in any manner on any label, when the appropriate TTB officer finds such State is associated by consumers with an American type whisky, except as a part of a name and address as set forth in paragraph (a) of this section.