my friend has been smoking cannabis for the past 9 years.he says he s not addicted and that he can leave it anytime he wants .he does leave it for some time but than starts again .he doesnt want to kick this habit .what do i do to make him give it up

You can beg and plead, and give ultimatums, but ultimately the decision has to be his. Though there is alot of debate over the addictive qualities to Marijuana, many people find it very difficult to give up.
Even if you were able to get him to "quit" for you, it would more than likely be only a matter of time before he was right back to doing it. An addict of any kind can not choose to stop for someone else's piece of mind, they have to have it in their minds to stop for themselves.

Well he's not going to give it up until he wants. If it bothers you, then you need to set boundries that you can live with. They could be:

a) you won't see your friend at all if they continue to toke
b) you will leave anytime your friend tokes in front of you
c) you won't be around them if they are high
e) don't be friends with this person anymore under any circumstances
d) do nothing and enjoy their friendship

Since you haven't said that you are married, dating, or in a relationship with this friend; other than the friendship, you don't depend on the friend for financial support, or have a commitment other than mutual friendship. So enabling behavior if withdrawn from your friend will likely not have the same affect as if it were withdrawn from family; unless your friendship means more than toking to them, which I doubt.

Personally I would continue the friendship, and if there are times that your friends indulgence causes them to miss work or screw up relationships or generally hold them back from either their own goals, or keeps them from being happy. As a friend you might remind them toking is getting in the way of them having the life they want. In time they may see that and want to quit on their own, or maybe they won't; but I would over time remind your friend that toking is serving no useful purpose other than to escape from life. If that's what they want, then ok, but if there is a desire within them to be something more than they already are you may have planted the seed of discontent which may have them reconsidering their behavior.

Just continue to love them as a friend and pick a boundry or two that is good for you and that will maintain your friendship. Remember it might be as simple as saying you are going home if he is high or tokes around you; if you are one of his few friends, he may not enjoy toking without people around and will do it less. Who knows? The point is, do what is good for you and maintain the friendship.