That is tough, he will only give it up when he is ready to. If you can live with it and still love him thats good. But if it is a relationship killer you have to know when it's time to leave. You could try telling him that you do not like it when he is doing hash, and why you don't like it. Ask him if he is willing to get help to stop, if he is not then you either have to live with it or leave it.

If something bothers you, there's no point in pretending it doesn't. Have you talked to him about why you think he should give it up? You can't make him stop, of course, but he may be more open-minded to your request if you give him reasons.

If he still says no, be careful. After all, you do not want to be arrested along with him if the cops come to his house and catch him doing it. At this point, you have two choices:

1)Stay--But only if you think you can put up with it and the relationship is otherwise a good one.

2)Leave, if you know that you'll never be able to accept his drug use.

Walk away. He's made his choice. What choice you make is up to you. Let me outline them clearly. Walk and live a decent life without drugs, stay and let him drag you down with him. And he will. After a while, it won't be hash, it'll be pills. Then he'll start shooting them. This story has variations, but stays the same if you get my meaning. You can see what is important to him and it isn't you. Be important to yourself and give yourself to a man that wants to put you first.
Good luck

He has made his position clear, he will not give it up. Now you have two choices, either live with him knowing he will continue to do this, or leave.

Personally, I would suggest to find another boyfriend.