I'm going to say it would be a violation because it wasn't designed to be used to physical protection and routing of conductors and isn't listed.
NEC 2011 344.2
344.2 Definition.
Rigid Metal Conduit (RMC). A threadable raceway of
circular cross section designed for the physical protection
and routing of conductors and cables and for use as an
equipment grounding conductor when installed with its integral
or associated coupling and appropriate fittings. RMC
is generally made of steel (ferrous) with protective coatings
or aluminum (nonferrous). Special use types are red brass
and stainless steel.
344.6 Listing Requirements. RMC, factory elbows and
couplings, and associated fittings shall be listed.
From American Piping Products:
ASTM A53 pipe (also referred to as ASME SA53 pipe) is intended for mechanical and pressure applications and is also acceptable for ordinary uses in steam, water, gas and air lines. It is suitable for welding and for forming operations involving coiling, bending, and flanging, subject to certain qualifications.