As said above reidentifying a grounded (neutral- white) conductor into an ungrounded conductor is perfectly legal per the NEC-
If you can get to a code book, (or maybe someone will post the passage in its entirety) its listed under 200.7(C)(1) in the 2014.
Here ya go:
200.7 Use of Insulation of a White or Gray Color or
with Three Continuous White or Gray Stripes.
(A) General. The following shall be used only for the
grounded circuit conductor, unless otherwise permitted in
200.7(B) and (C):
(1) A conductor with continuous white or gray covering
(2) A conductor with three continuous white or gray stripes
on other than green insulation
(3) A marking of white or gray color at the termination
(B) Circuits of Less Than 50 Volts. A conductor with
white or gray color insulation or three continuous white
stripes or having a marking of white or gray at the termination
for circuits of less than 50 volts shall be required to
be grounded only as required by 250.20(A).
(C) Circuits of 50 Volts or More. The use of insulation
that is white or gray or that has three continuous white or
gray stripes for other than a grounded conductor for circuits
of 50 volts or more shall be permitted only as in (1) and (2).
(1) If part of a cable assembly that has the insulation permanently
reidentified to indicate its use as an ungrounded
conductor by marking tape, painting, or other
effective means at its termination and at each location
where the conductor is visible and accessible. Identification
shall encircle the insulation and shall be a color
other than white, gray, or green. If used for single-pole,
3-way or 4-way switch loops, the reidentified conductor
with white or gray insulation or three continuous
white or gray stripes shall be used only for the supply
to the switch, but not as a return conductor from the
switch to the outlet.