Generally speaking, in international track and field I have noticed it is a lot harder to get a call like this made than it would be in the NCAA, for example. I think it would have to be an obvious and egregious impedance to get a winner disqualified. Look at the prelims of the 1500m. During the big Baala debacle they only put through the guys that were literally pulled backwards by Baala. They did not put through the two individuals who fell in the back and were out of contention. If that were the NCAA, they would have put through everyone.
As for Lagat, I can't understand how so many are this narrow minded about his citizenship. What if, instead of running in these championships or the Olympics, he wanted to join the Army and go to Iraq? Would you slam him for that too because he is not a "real" American?
He came to America in search of a better life(school, coaching, opportunity), earned citizenship, sat out his mandatory IAAF waiting period, and wants to represent his country. That is what this country is based on. Of all the athletes interviewed in Osaka he is really the only one that I can recall that said they did it for America and the American people. It was a refreshing break from the norm.
To borrow from the book of Rick Pitino, Billy Mills ain't walkin' through that door. Other than Native Americans, we are all at least descendants of immigrants and should be happy he has realized this is the best country in the world despite its flaws and wants to become a part of it.
This whole debate kind of reminds me of a person that was born Catholic(for example) but doesn't practice, yet feels superior in their faith compared to a converted Catholic that does. To me, both citizenship(note NOT nationality) and religion are not based on seniority, but on how you practice. Lagat proved to me that he is a practicing American and I was proud of him.