Designated Hitter: the actual rules

http://mlb.mlb.com/mlb/official_info/official_rules/batter_6.jsp

6.10
Any League may elect to use the Designated Hitter Rule.

(a) In the event of inter-league competition between clubs of Leagues using the Designated Hitter Rule and clubs of Leagues not using the Designated Hitter Rule, the rule will be used as follows:
    1. In World Series or exhibition games, the rule will be used or not used as is the practice of the home team.
    2. In All-Star games, the rule will only be used if both teams and both Leagues so agree.
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The rest of 6.10 describes the rule during the game.  It occurs to me that in American Conference parks that the two managers could reach a gentleman's agreement not to use the DH in a particular game.  It's use is not mandatory.

If Yankee manage Joe Girardi decided not to use a DH in this afternoon's game at Fenway Park, that would be allowed.  Girardi, of course, would not do that unilaterally.  However, if Red Sox manager Bobby Valentine decided to do the same, then they could play the game with no DH.

I wonder if the reverse could work.  If two National Conference managers wanted to both use the DH, what would the umpires decide?  Since the so called National League did not "elect to use the Designated Hitter Rule" the umps would probably tell the managers that it was not allowed.  But if common sense prevailed and the interpretation was that the two conferences were part of one Major League, then it might work.

Hey, this beats whining about it.