I need to make sure alcohol isn't advertised to underage users or in countries / regions where alcohol is illegal.
Ideally using MaxMind geo codes but I'm sure I could map from any geo system.
One option is to use a Github repo (fork your own) that other users can contribute to, which will help keep it up to date.
https://github.com/aihpos/drinkingage/blob/master/drinking.csv
Although for regulatory purposes, this may not be sufficient. Also, this is a really nuanced topic, so may be tough to capture with 100% coverage.
For example, Switzerland:
18 for spirits 16 or 18 for beer and wine depending on the Canton
Any csv can be turned into a json API, although this example is a bit overkill.