It was a simplification on my part. If you want to be precise, then chaptalisation (the process of regulating alcohol quantity using sugar) is illegal in south of France vineyards, forbidden everywhwere when mixed with acidification processes, and allowed but under very strict conditions otherwise in "septentrionales" vineyards (which I have no idea how to translate in English).
That's not true. Adding sugar is even part of some AOP. It's used to regulate the amount alcohol in the finish product.