or see if he learns through osmosis. Spit in his face, then hit him with your rulesbook.
It really saddens me how often we get that here on the forums..." I showed him the rules but he insists that they don't apply, oh, and he won't back it up with another cited rule".
While some of it falls onto us players to police ourselves and spread info as we become aware, I believe a large factor of it sits squarely on GW's shoulders for not putting out erratas to all the changes they make (read as new printings of codexs, making you buy the new one for the new rules) and answering basic screwups (like wargear book listing termies as a 3+ 5++ save) or often questioned rules (living metal says all sources are treated the same, so powerfists shouldn't work) instead of playing by and misprinting rules (IC's joined to deepstriking squads and monoliths and...and...).
Anyways, just my rant, sorry, carry on, nothing to see here.