Can anyone tell me whether I need the NFL's permission to sell photos of NFL players I took w/ my own camera during the game? I would sell these for a profit.
From my knowledge, all sports leagues will exploit every penny they can from their product. The ticket policy that anyone entering the ballpark (which is sometimes contained in highly questionable inclusions that may appear at the stadium) is what governs what you can and cannot do at a game. From what I know, the terms of the ticket are the purchase and sale contract terms and they prohibit the sale of photographs that may be taken at a game by a fan. So why can you buy pictures from other sources? Because of agreements the sports team may have with the press, private photographers, etc. and would include the team being paid.
In addition to ticket policies, there may also be rights of publicity that a player may have that could prevent fans from selling pictures they took of players. There may also be questions of trademark law that could be asked but it's not really the determining factor in what prevents sports fans from selling pictures they took at a baseball game, basketball game, football game with their own camera.
While the way the information may be presented is unclear, but are you going to fight a case against you?
http://mlb.mlb.com/nyy/ballpark/guide.jsp#Cameras and Video Equipment
CAMERAS AND VIDEO EQUIPMENT
Single-frame flash photography is permitted. Tripods, extended length zoom lenses, other professional camera equipment, movie cameras and any other video or audio recording equipment are not permitted in Yankee Stadium.
Guests are not permitted to transmit or aid in transmitting any account, description, picture, video, audio, reproduction or other information about any games.
There you have it. Personal pictures taken with a cheap, non-zoom camera are able to be taken without consent. However, "guests are not permitted to transmit.... picture... about any games" - this would be a prohibition against you selling your photos.
There may be other explicit prohibitions although most of the ticket policies seem to contain only security policies and not the remaining portions of your contract of sale terms. I hope this answers your question.