New Rules

So I have done a no spawning rule for my server. Its my new rule. Only me and another person can use the spawning. Sure they don't spawn in front of me. But when I get home from school and check the log I see spawners. I confront them and they say they don't spawn. But clearly they did. They get pissed at me and just say K. And make me feel like the bad person. So they keep spawning. I don't know if I should ban them or take their modding away. If I take their mod rights away they never come back and I wanna keep them wothout spawning. What do I do?