Moving them to the woods will in no way harm the woods. If a few snails were going to the destroy the forest it is doomed anyway. However, if you move them only a 100 feet or so they are not apt to return to your garden. Fishermen often use worms, crickets, grasshoopers etc. for bait and release that not used. No harm done. The problem I see is if you attempt to move them across international borders or the California state line. California is the only state I know that cares (perhaps with good reason). Hedgehogs? England? Still doubt there is a law preventing hauling of wild and unrully snails.