I was actually under the impression that it is allowed depending on the length of the conductor, but it seems you are right. The NEC Table 15(B)(16) shows the maximum allowed ampacity of 14 AWG cables is 20 amperes, BUT... there is a footnote that states the following:

> * Unless otherwise specifically permitted elsewhere in this Code, the overcurrent protection for conductor types marked with an asterisk shall not exceed 15 amperes for No. 14 copper, 20 amperes for No. 12 copper, and 30 amperes for No. 10 copper, after any correction factors for ambient temperature and number of conductors have been applied.

I could've sworn there were actually some cases where it was allowed, but apparently not, or if there is, I'm not finding it. Seems like for 14 AWG cable the breaker can only be up to 15 amperes.