Depends on the intent of the snail as to it's legality. Just like it is illegal to own a dog for dog-fighting purposes.
In some backwards areas people will put two snails into an aquarium and taunt the snails with jibes about how easy their mothers were and how many eggs they laid all over the place.
Crowds of people will them gamble, drink, and chant "Jerry... Jerry... Jerry..." whilst waiting for the snails to fight.
These snails arn't like your typical snails though- they've been bred and trained from an early age to be vicious- brutal and murderous... occasionally one will even approach the other for reasons other than to mate.
The last snail to die is considered the winner- and the frantic crowds will then settle their gambling debts and dispurse before the police arrive.