What laws are there for feeding animals to other animals? Example: pigs to crocodiles, rodents to dogs, etc?

As long as it's species appropriate and not on the banned animal list, then many pets REQUIRE meat to live. Many snakes eat mice and rodents. Cats are obligate carnivores and must eat meat to live. Dogs require a meat based diet. As long as the meat animal being fed is not cruelly treated, and not on the endangered species list, it's not only acceptable to do, but often necessary to do.

Laws are different in different countries. No laws against that in US other than using red list animals as feeders and includes those defined by the migratory bird act.

IE: live mice to snakes is common.

It a depends on where you live, what animal and what your intending to feed it, is it live, was it wild? Frozen or purchased from legal market?

Some animals are illegal to slaughterer while others may be endangered in one state yet consider a nuisance in another.

Check with authorities if what type of bait your intending to use is legal to have, legal to use in fresh or frozen form and what animal your intending to feed.

Depends on where you live. Where laws regarding that exist they are usually based on anti-cruelty legislation so feeding a live pig to a croc would be a violation.

In my city a pet store owner was charged for feeding a live mouse to a piranha which was deemed unnecessarily cruel. I believe the UK prohibits feeding live rodents to snakes except when necessary.

No cops watching, live by your rules, you wanna feed your dog raw meat honestly who cares? My old dog would eat anything, really nasty sh*t if I weren't there to take it off him, like semi-decayed seagull. Nasty lil bugger.

A teacher in Idaho fed a sick puppy to a turtle in front of the classroom and got in all sorts of trouble

Well, I know you do not feed rodents to a dog.