The question of what type of wiring method to use when concealing conductors for low voltage lighting come up often on the forum and until now the standard answer has been that we are required to use a Chapter 3 method, that will change.
There is a change in the 2005 NEC that will now allow other than chapter 3 wiring methods to be run concealed for low voltage lighting systems.
411.4 Locations Not Permitted
Lighting systems operating at 30 volts or less shall not be installed in the locations described in 411.4(A) and (B)
(A)Where concealed or extended through a building wall unless permitted in (1) or(2):
(1)Installed using any of the wiring methods specified in Chapter 3.
(2)Installed using wiring supplied by a listed Class 2 power source and installed in accordance with 725.52
(B)Where installed within 3.0 m (10 ft) of pools, spas, fountains, or similar locations, unless permitted by Article 680.
IMHO this is a good change, when using a class 2 power source 14 AWG is overkill (in most instances) and harder to conceal.