They are certainly legal in the UK, but are not in some states of the US. I have four. If they lay eggs, you can dispose of them by freezing them.
They are edible, and are often on sale in markets in the London area.
There is a good site called snails online which has a lot of info (including recipes!).
They make fascinating pets, if looked after properly. They need to be kept warm in the cold weather but not allowed to dry out as they dehydrate and go into a sort of 'shut down'.
They eat mainly lettuce (round) and cucumber, but also other things such as sweetcorn. They also need cuttlefish to provide calcium to keep their shells hard. They have a sort of rasping action and wear it away. You can feel this if you hold them on your hand.