My fears are substantiated, it seems.
Having read
this on RPGPundit's blog...
1. No Rule 0. Yes, GMs can create house rules, but it does not appear that they can make rulings on the spot. In fact, in the section on how to deal with Rules Lawyers, one of the things that is most notable is that it DOESN'T tell you that you can just tell him to shut up or **** off, or that you as GM overrule his knowledge of the rules. No, apparently you're supposed to apologize if you've made an error, or you're allowed to put off discussion till the end of the session, and the rules lawyer is allowed to take all the time he wants to look up the rule while his character exists in a limbo (and cannot be harmed by the monsters or anything else).
...my worst fears have been apparently been realized. I should see the DMG this weekend to confirm this for myself.