What must appear, and where
On this page11
On the brand label
The brand name, and the class, type or other designation. Those two are tied to it.
Anywhere on the container
The name and address, the net contents and the alcohol content. Any label on the container, which means a back label can carry all three.
Which is a real design freedom
A spirits label has to hold brand name, class and type and alcohol content in one field of vision. A wine label does not, so a minimal front and an informative back is a lawful layout here.
The sulfite declaration
"Contains sulfites" or an equivalent statement, on a front label, back label, strip label or neck label, where sulfur dioxide is detected at 10 parts per million or more.
Ten parts per million is low
Low enough that a great many wines carry the declaration, including ones where no sulfite was added, because fermentation produces some. Testing rather than assuming is the honest route.
Other declarations with their own rules
Cochineal extract or carmine must be stated if used, on a front, back, strip or neck label. FD&C Yellow No. 5 may appear on a brand or back label.
And the Government Warning on top
Separate from all of the above, with its own type size by container volume and its own contrast requirement. The spirits property covers it in detail.
Plan the back label as a real surface
Because here it can carry most of the mandatory information. That makes the back label a layout problem rather than an afterthought, and it is where a lot of wine labels are won or lost.
Which elements move is a design decision, once
Deciding early that the name and address, the net contents and the alcohol content all live on the back frees the front entirely. Deciding it late means redrawing both labels.
Net contents moves to the front for a non-standard fill
Which is a detail worth noting: where the fill is not one of the standard sizes, the placement rule tightens. For almost every product that will not arise, and for the one where it does it is a surprise.