The FARs address minimum fuel levels when you arrive at your destination.
If you have less than the required amount when you land, you are in
violation.

I know of no such rule under part 91 of the US regs. (I am not familiar
with part 135 ops). You are required to carry sufficient fuel upon
takeoff to make it to your destination with reserves, but once in the
air, if you need the reserves, you may use them. That is what they are
there for.

If you go too far into your reserves and crash, having passed up
opportunities to not crash, the FAA may get you on "careless or
reckless", but simply landing having used some of your reserves is not a
violation AFAIK.

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
for Email, make the obvious change in the address.