This question already has an answer here:
Some time ago I stopped running/playing modern RPGs like Pathfinder and 4e in favor of White Box S&W. I like S&W because of the bare-bones nature that leaves many things up to my discretion as a DM, but the thing that gets on my nerves is something I have had problems with since I ran modern. Players stopping me during combat when I have made a ruling asking to "see the book". I expect this in modern because there is a rule for "everything" and most of the time at the table is spent whining and rules lawyer-ing (at least in my experience). I don't feel like players have a right to look at the book just like the DM has no right to control the actions of a PC against the players will.
I guess my question is, how do I tell players they can't "see the book" in the most effective and nicest way possible.