Here are links to NFL Constituion and bylaws and specific passage where it cites how it applies to owners and the CBA and how it is an agreement between management and the players.....
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NFL Constitution
http://static.nfl.com/static/content/public/static/html/careers/pdf/co_.pdf
Article II
Purposes and Objects
2.1
The purpose and objects for which the League is organized are:
(A) To promote and foster the primary business of League members,
each member being an owner of a professional football club located in the United States
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CBA
https://nfllabor.files.wordpress.com/2010/01/collective-bargaining-agreement-2011-2020.pdf
xiv
PREAMBLE
This Agreement, which is the product of bona fide, arm’s length collective bargaining, is made and entered into as of the 4th day of August, 2011 in accordance with the provisions of the National Labor Relations Act, as amended, by and between the National Football League Management Council (“Management Council” or “NFLMC”), which is recognized as the sole and exclusive bargaining representative of present and future employer member Clubs of the National Football League (“NFL” or “League”),
and the National Football League Players Association (“NFLPA”), which is recognized as the sole and exclusive bargaining representative of present and future employee players in the NFL in a bargaining unit described as follows…