Again, please don't take this as being too harsh, but I think you aren't giving your 4 year old enough credit. At the tender age of 4, he has already learned how to manipulate you. Every time you pick up those toys, you are teaching that child that the more he tells you no, screams, cries, or whatever it takes, he gets his way. What do you think is going to happen when that child is 16? He is going to either be totally ignoring you or telling you what to do. You have to teach them respect and obedience at a young age. If this child is already telling you no and refusing to do what you tell him on a regular basis, you have some work to do. No, I don't think it's too harsh to take away his outside priveledges. You have to do what works. You also need to realize no matter how you choose to retrain this child that at the beginning it's going to be difficult. He is probably going to tell you no, cry louder and act out worse than he ever has because he knows that has always worked in the past. What YOU have to do however, is do NOT give in. Stay with him until everything is picked up. Be prepared to spend possibly hours depending on how stubborn he is. When you are at your wits end, keep in mind if you cave and do it yourself, he has WON. And yes, he will consider this a victory. He will KNOW he can control you with his tantrums. Good Luck and you can do it, it's just going to take time and lots of patience and love.
God Bless,
Sherry