[Goose]

ESPN won't like it, but a 1 loss SEC team that is not the conference champion can't be selected over 1 loss conference champions from the B1G, PAC-12 or Big-12. If that should happen, it will blow up the agreement between the power 5 conferences.

Is this codified in some sort of contract language?

The answer is "sort of". The committee operates under agreed-upon guidelines. The committee set the guidelines and the conferences agreed to them. I am sure there is no real "article 50 exit" clause in that agreement. However, if the guidelines are violated in an obvious way, I believe there would be enough hated and discontent generated that the idea of a selection committee wouldn't survive it. The guidelines clearly say that conference championships count as tie-breakers when teams have equivalent records. The consequences of not honoring that understanding would render the selection process a travesty, and everybody in the country would know it. It may already be that, but it isn't clearly demonstrable. They have never made a selection yet that was directly contradictory to a guideline.
The members of the committee are diverse enough that it is improbable a majority would go directly against a guideline. Sticking to the "rules" is the course of least resistance. However, if a PAC-12 champion has two losses and an SEC runner-up has only one loss, it is NOT a direct violation of the guidelines to leave out the PAC-12 champion ad choose the 1 loss SEC runner-up instead. Controversial, it would be, but not clearly a breach of the "rules". If both teams have one loss, it is possible to argue their records are not "equivalent" because a loss in the SEC championship game is less bad than a loss in the regular season to say USC, and that trumps a conference championship. However, I think that would be such a hard sell that the committee isn't ever going to do such a thing. It might even be worth the problems it would generate if it expanded the field to eight teams sooner rather than later. What wouldn't work would be for example, the  ACC, and SEC to say "Too bad, agreements are meaningless. We control the agenda". The committee provides at least a vernier of objectivity. If that is removed, it isn't a "national championship".

[Goose]

ESPN won't like it, but a 1 loss SEC team that is not the conference champion can't be selected over 1 loss conference champions from the B1G, PAC-12 or Big-12. If that should happen, it will blow up the agreement between the power 5 conferences.

Is this codified in some sort of contract language?

The answer is "sort of". The committee operates under agreed-upon guidelines. The committee set the guidelines and the conferences agreed to them. I am sure there is no real "article 50 exit" clause in that agreement. However, if the guidelines are violated in an obvious way, I believe there would be enough hated and discontent generated that the idea of a selection committee wouldn't survive it. The guidelines clearly say that conference championships count as tie-breakers when teams have equivalent records. The consequences of not honoring that understanding would render the selection process a travesty, and everybody in the country would know it. It may already be that, but it isn't clearly demonstrable. They have never made a selection yet that was directly contradictory to a guideline.
The members of the committee are diverse enough that it is improbable a majority would go directly against a guideline. Sticking to the "rules" is the course of least resistance. However, if a PAC-12 champion has two losses and an SEC runner-up has only one loss, it is NOT a direct violation of the guidelines to leave out the PAC-12 champion ad choose the 1 loss SEC runner-up instead. Controversial, it would be, but not clearly a breach of the "rules". If both teams have one loss, it is possible to argue their records are not "equivalent" because a loss in the SEC championship game is less bad than a loss in the regular season to say USC, and that trumps a conference championship. However, I think that would be such a hard sell that the committee isn't ever going to do such a thing. It might even be worth the problems it would generate if it expanded the field to eight teams sooner rather than later. What wouldn't work would be for example, the  ACC, and SEC to say "Too bad, agreements are meaningless. We control the agenda". The committee provides at least a vernier of objectivity. If that is removed, it isn't a "national championship".