Where does it say that in Article IV - No Strike/Lockout/Suit of the CBA??
Section 1 . Except as otherwise provided in Article V (Union Security), Section 6, neither
the NFLPA nor any of its members will engage in any strike, work stoppage, or other concerted action interfering with the operations of the NFL or any Club for the duration of this Agreement, and no Clubs, either individually or in concert with other Clubs, will engage in any lockout for the duration of this Agreement. Any claim by the Management Council that the NFLPA has violated this Section 1 will not be subject to the grievance procedure or the arbitration provisions of this Agreement and the Management Council will have the right to submit such claim directly to the courts.