Somewhat related to being forbidden might be 314.28A2 EX>
Quote

Exception: Where (l raceway or cable entry is in the wall
of a box or conduit body opposite a removable cover; the
distance from that wall to the cover shall be permitted to
comply with the distance required for one wire per terminal
in Table 312.6(A).


Which is dictating a distance to not only gutters, but LB's as well....

~S~