Idiom: a complicated (apparently
insoluble)
problem.
E.g.,
President Bush's plan to foster cooperative efforts between government and religion-based groups may open a legal can of worms.
"The explosive growth of the Net music business also has opened up a copyright and licensing can of worms." --CNET, April 15, 1998
Metaphor comes from a
container of
bait, which would have a
wriggling, tangled mass of
worms, from which it is difficult to
extract a single worm required for baiting a
fishing pole.