First
Well now having read the contract as provided by the Salt Lake Tribune...Leaving the WAC was in fact an express breach of provision 4. However, provision 5 set the damages of said breach of provision 4 at $5 million. Thus provision 5 is a "liquidated damages clause" and I could not imagine more than this amount to be recoverable.
"5. Any WAC member (except Louisiana Tech or Boise State) or BYU shall pay a penalty of $5 million in the event it violates the terms of paragraph 4 herein unless the conference that is joined has current (as of the time joined) automatic access for its league champion into the bowl championship series (BCS). Said payment will be made within 60 days from demand from the WAC."
Second
An argument that is sure to be raised lies in the text of provision 6.
"6. In the event that any current WAC member, (except Louisiana Tech or Boise State), or BYU leaves the WAC in accordance with the provisions of paragraph 5 herein, the terms of this resolution are terminated."
-The argument will be over whether both schools leaving owe $5 million each. Provision 6, seems to require provision 5 to be fulfilled before the agreement is terminated. Since the first school leaving had not paid the $5 million as of the time the second school left the conference...it seems very debateable whether the contract was in fact terminated upon the first school leaving.
Third
Finally, this contract (as has been mentioned and according to provision 4) seems to only take effect upon BYU's agreement before Sep.1. This is called a contigency. If BYU never agrees before Sep. 1, then according to contract principles no contract would have existed. However, the WAC has a pretty good argument that Nevada and Fresno owe the money regardless, because they breached provision 5 before the contigency in provision 4 had expired.
"4. The WAC and its members and BYU, agree that all current members of the WAC (except Louisiana Tech and Boise State, which has already given notice of its withdrawal) will not join any other conference or athletic conference from the date of adoption of this resolution through June 30, 2016, contingent upon BYU agreeing that it will not join any other conference or athletic conference from the date of entering a contract with the WAC through June 30, 2016"
Finally
I just wanted to say one last thing. For this agreement representing large entities and large amounts of money, it is poorly drawn up. The liquidated damages provision only applies if a member of the WAC leaves for a non-bcs conference. According to provision 4, the contract is breached if a member leaves the WAC for any conference....so WTF are the damages if a WAC team had left for a BCS league. Just extremely odd that a liquidated damages provision would be included for one breach but not for another very similar breach.
I think the drafters meant a penalty would only be enforced for a member leaving to a non-bcs league. But who knows with this ambiguity???
Note: While I am a licensed attorney, my thoughts should not be construed as legal advice and rather just my opinion of a contract in which I am not involved in nor have all facts thereof.