I have always used GFCI circuit breakers,
or GFCI receptacles for a local room extension.
You can work your way through these cites:
ECG & two wire cable: 250.130(C)
382.10 Uses Permitted. Nonmetallic extensions shall be
permitted only in accordance with 382.10(A), (B), and (C).
(A) From an Existing Outlet. The extension shall be from
an existing outlet on a 15- or 20-ampere branch circuit.
Where a concealable nonmetallic extension originates from
a non?grounding-type receptacle, the installation shall comply
with 250.130(C), 406.3(D)(3)(b), or 406.3(D)(3)(c).
382.12 Uses Not Permitted.
Nonmetallic extensions shall not be used as follows:
(1) In unfinished basements, attics, or roof spaces
(2)
(3)
(4) Where run through a floor or partition,
or outside the room in which it originates