I got the feeling that you were on the road alot and I understand your situation. You leave the keys with mom in case the car needs to be moved for some reason (blocking drive way, etc) or if mom's car breaks down, etc. I get it.
That said, some of the posts here are right - he will not learn and will not move on with his life if he isn't forced to. I assume he's still living with mom and mom works so she can't keep an eye on him, so he nabs the keys and does his thing.
One option would be to put the car in storage while you're gone. Lots of the places that you can rent storage for your household items also have places to park cars, boats, and RV's. Put the car there, even if it costs you $50/month. That way the car isn't in the way at mom's place, he doesn't have the keys and even if he did, he doesn't know the code to get into the storage place. Of course you could take the keys with you, pack in them in your carry-on luggage and be done with it.
As someone who went through the "useless sibling" thing, tough love is the only way to make them get on with things. As for calling the police, I actually did have to do that at one point on my own father - it was not a pretty picture. Don't go there unless you absolutely have to.
That said, some of the posts here are right - he will not learn and will not move on with his life if he isn't forced to. I assume he's still living with mom and mom works so she can't keep an eye on him, so he nabs the keys and does his thing.
One option would be to put the car in storage while you're gone. Lots of the places that you can rent storage for your household items also have places to park cars, boats, and RV's. Put the car there, even if it costs you $50/month. That way the car isn't in the way at mom's place, he doesn't have the keys and even if he did, he doesn't know the code to get into the storage place. Of course you could take the keys with you, pack in them in your carry-on luggage and be done with it.
As someone who went through the "useless sibling" thing, tough love is the only way to make them get on with things. As for calling the police, I actually did have to do that at one point on my own father - it was not a pretty picture. Don't go there unless you absolutely have to.