The Citadel is an archive of information for George R.R. Martin's A Song of Ice and Fire.
New to the series? Read our spoiler-free review of A Game of Thrones.
At what age does a boy in Westeros legally become a man?
16
And how does age effect the enforceability of oaths? Specifically, if Jon Snow was 14-15 years at the time he swore his oaths to the Night Watch can he avoid them as he was, maybe, a minor?
No loopholes. Once you say the words, you're in.
That being said, the Watch would not give the oath to a boy that was seriously minor, like a 12 year old.
The Westeros network consists of several different sites, including a forum and a wiki, for all your A Song of Ice and Fire needs.