What makes certain alcohol beverages gluten-free? Well according to an article on AlcoholProfessor.com ultimately all distilled spirits are gluten-free.

If you have celiac disease or an intolerance to gluten, then the good news is that distilled spirits are safe for you to drink.

In the USA a ruling has been passed that only spirits made with gluten-free products can be classified as gluten-free so check for this on the label when shopping.

Read more at https://www.alcoholprofessor.com/blog/2013/04/02/what-really-makes-a-spirit-gluten-free/