From the 2005NEC:
(11) In wet locations where any of the following conditions are met:
a. The metallic covering is impervious to moisture.
b. A lead sheath or moisture-impervious jacket is provided under the metal covering.
c. The insulated conductors under the metallic covering are listed for use in wet locations.
The code Changed in 2008 it's present verbiage, and also first prohibited FMC in wet locations, too.
Could it be you bought cable pre-2008?
