We heard from someone recently who had to endure a lot of pain because a family member just could not cure, or would even address, his gambling problem. When finding folks like that, it is rather dicey in terms of the advice one can give, because obviously if you steer someone wrong, it could have disastrous results.
Mistakes are very easy to make. One of the things that will not work is if you try to "discipline" the problem gambler. Punishment and control are a couple of things for which you are going to find some resistance, almost without question. In many ways, the gambling addict is like a child, in that they are going to contradict you, no matter what you say, except in some instance when you encourage and even enable their gambling, in which case they will be happy to oblige.
If you are a concerned person, you cannot make believe the problem does not exist, or that it will somehow go away. It won't. But that does not mean you should not make the problem gambler aware that you are aware of the issue, and how it is affecting YOU. Gambling addicts are not sociopaths; in fact, in many cases they are people with very deep feelings of low self-esteem and are not in any way unconcerned about others. MANY people who have sought help for their gambling problem have done so because they came to the realization that their behavior was having some deleterious effect on a loved one. So in no way should you be afraid to let someone know that they are adversely affecting you.
And don't be afraid to offer help as well. That goes for whatever kind of POSITIVE help it is. Let them know that you will be there for them "if and when." At the same time, however, do not assume their problem. DO NOT acquiesce to what they want under their promise that they will stop soon. Remember that addicts, whether it is alcohol, drugs or gambling, are very good con artists, even if they don't mean to be, because the subject of their addiction is so important to them that they are willing to do anything or say anything to satisfy that addiction.
So why you can't lock someone down, you also can't encourage or enable their efforts. have a very good idea what you want YOUR situation to be, and use that as the anchor from which you will help anyone WHO WANTS HELP.