Conversation so far:
Who initiated the ban?
Joseph Carr made it one of his first goals as league president to impose a strict ban the use of college football players.
When was the APFA college player ban initiated?
The ban was initiated around 1921.
How did Carr enforce the APFA college player ban?
Players lost their amateur status and were barred from further college football participation.
What else did Joseph Carr do to enforce the APFA college player ban?
In January 1922, Carr responded with the severest possible action, kicking the Packers out of the APFA.
Were any other teams fined besides the Packers for violating the APFA college player ban?
The Cardinals were fined $1,000 for their prior knowledge of the violation, and Cardinal player Art Foltz was temporary banned from the league.
How long was the APFA college player ban active?
Was there any opposition to the APFA college player ban?
What other interesting information is there about the APFA college player ban?
The issue arose again when Red Grange, star halfback of the University of Illinois football team, signed with the Chicago Bears.
Why was the ban initiated?
In the early 20th century professional teams would sometimes pay college players to play for them, which was considered questionable ethically, resulting in taint being associated with the professional game.

Question: How was it discovered that college players were being paid?
Self-contained rewrite: How was it discovered that college players were being paid?