I do not practice in Washington, but I would be skeptical that you could get a restraining order if they are only consuming illegal drugs. You you probably need to do is call the police and have them arrested. if abuse is present you might be able to obtain help at a domestic violence shelter.
It is unlikely that you will be able to get a restraining order of any kind. Unless your family member is harassing you or committing acts of domestic violence. If either of these are the case, you should consult your local court clerk immediately, who can guide you through the process of getting a protection order put into place.