@Ez0 Having them "agree" to the fine and actually paying the fine are very different things. You will likely have to request the amount through the Airbnb platform; however, the guest has the right to decline to pay. At that point the only option you have is taking them to small claims court as Airbnb's Aircover policy is more in place for damages, not rule breakages.
A few issues immediately stand out to me though, which may make your quest to get these funds difficult. First, yes, you most definitely have the right to asks guest to leave if they break rules. However, when this occurs you should also immediately open a case and notify Airbnb support as their reservation will need to be terminated and the incident should be documented to further protect you. A verbal he said she said doesn't always hold up well.
Second, recording someone without their permission or knowledge is not going to work in your favor. It will likely support their claim of being in an uncomfortable situation. Again, the best way to handle an Airbnb issue is calmly notify the guest of the issue, verbalize your intentions/expectations, and contact Airbnb support to assist and document the issue.
I once had a similar situation to you where a young couple smoked weed in their room. I immediately contacted Airbnb and disclosed the issue and had a case opened. I then approached the guest, let them know what the violation was and informed them the reservation was being cancelled as a result of this. I know all guests are not going to be pleasant with situations like these but do your best to stay calm and stick to your policy.
