The closest you can come is 91.9, so there is nothing to "trump"
because the POH wording is not consistent between manufacturers or
models (and, as some have pointed out, some POHs say nothing about
icing).

But some do, and the wording inconsistency doesn't seem relevent when
the meaning is clear. My Seneca says "Not approved for known icing",
and I don't think that ATC procedures can therefore make it legal.

And there is always 91.13 (Careless or Reckless) for the FAA to fall
back on.