1903 National Agreement and minor league players
 

I was reading a NYT from 1903 on the National Agreement and it said that "farming" from of a player from a major league team to a minor league team was prohibited. I looked it up and sure enough here is what is said.

"SEC. 4. The practice of farming is prohibited. All right or claim of a major league club to a player shall cease when such player becomes a member of a minor league club, and no arrangement between clubs for the loan or return of a player shall be binding between the parties to it or recognized by other clubs."

I know that teams would send players to Omaha for "more seasoning" and Omaha would send players to teams in the class "D" Nebraska State League and then recall them when needed. It is well known that in the 20's the Cardinals established their farm system. I know that Landis made a number of Cardinal farm hands free agents in 1937.

Was the rule just ignored or was it revised at some point? Can someone point me to a book or explanation of this issue or the 1937 situation.