This is what Atkins says:

You should not drink alcohol during Induction, but you can drink moderate amounts of alcohol during the Ongoing Weight Loss, Pre-Maintenance and Lifetime Maintenance phases of the Atkins Nutritional ApproachTM. When given the choice, your body will burn alcohol for energy before it burns fat. But alcohol does not act as a carbohydrate so it will not interfere with burning fat in the same way that sugars and other carbohydrates do.
Alcohol consumption may also increase yeast-related symptoms, such as bloating, gas and cravings for sweets, and can therefore interfere with weight loss. Beer, which contains yeast, probably has the most yeast-forming components of any alcohol. An occasional glass of wine or vodka is the best choice. Scotch and other grain-based spirits are more likely to promote yeast problems.

So basically, in ketosis avoid the booze and after that be aware that while you are boozing you ain't losing!