How to spot future brother in laws potential drug use?

well fellow TWers he couldn't last more than two days without breaking a rule..such a shame. I'm still here at school(bought 30min away from my house) Fiance just texted me said she caught him smoking in the house with his friends. She immediately told all his friends to leave, he tried to leave with them. She told him to stay, so she could confront him. He said our rules are bullshit, she said he was acting weird and suspected he was on something else. I do regret letting him stay for these past two days, but atleast now she saw it directly. She called her dad to come over and pick him up. But before that she made him call his girlfriend at work and explain why they are being kicked out..I feel bad cause its family, but he broke the rules hes an adult. I'm changing the locks tomorrow, his girlfriend can come over and pack up the shit but he's not allowed back in the house.