Channels 12 and 13 are disabled in the wireless-regdb as FCC regulations imposes strict limits on interference in the neighboring restricted band, but folks have not come up with a practical and tested power limit for the two channels to guarantee this.
See the commit for the full rationale: http://git.kernel.org/wens/wireless-regdb/c/ede87f56c6c69652d30e09ce9d9fc07b8dea3388 ChenYu
