According to Andy Hill :

Drifting a bit, but does the NEC even address temporary stuff like "extension
cords" (other than the requirement that extension cords are not to be used for
permanent wiring)? Seems like more of a UL or OSHA issue.

Strictly speaking, this is a "c*&p, my circular saw caught fire" issue ;-)
NEC doesn't cover this sort of wiring per-se, and "officially" this is
a UL (or CSA or CE or...) issue. However, this isn't an anal safety
rule sort of thing, more of a "it _will_ bite you"/"laws of physics"
sort of thing.

[The NEC does have some stuff to say about temporary wiring. Ie:
temporary wiring in many cases _is_ covered by NEC, ie: "event"
temporary wiring.]
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.