Back in my younger days, I had admin privileges on a UT2k4 server. There was usually a nice group of regulars around. If I was playing and one of the regulars reported someone suspicious I could go into spectator mode, watch through their point-of-view to make sure, record it to a demo file for evidence, and then immediately ban them.
Beyond the community of regulars on our own server, we had good contacts with admins on other servers that catered to a similar gamestyle. We'd regularly exchange ban-lists with them. (I.e., there was kind of a meta community of server operators.)
I realize that that doesn't scale the same way as modern approaches, but the modern approaches also feel like they're trying to use technical means to solve a social problem.