<human>: A little back story:

My 19 y.o. brother is smoking weed. My parents are anti-drugs (including softdrugs) and kicked him out after being caught with drugs (the second time). After this, I decided to offer him the spare room in my house, with the promise to not bring drugs into my house. He could smoke it at a friend, but my SO doesn't want it in the house.

Not long after he moved in, I found out that he brought drugs to my house. He told me he didn't know where to store it elsewhere. I reminded him of the promise not to bring it in the house and told him he could smoke the remainder he had on him outside. He promised that he would keep any new weed at friends. This happened 5 days ago.

Yesterday, my SO snooped around his room (without my knowledge) and found a small amount of weed in his bag. Right now, I don't really know what to do. On one hand, I don't approve the snooping around, as I think it's an invasion of privacy. On the other hand, I'm really disappointed that he didn't keep his promise to me.

So, do I need to confront him? If so, what should I say to him? And how will I know he will keep the promises he makes in the future?

Can you summarize the given text in a few sentences?
<bot>: Took my brother in house with the promise he wouldn't keep drugs in the house. He ignored this promise twice. Do I need to (and how do I best) confront him?