I'm not familiar with the term "Thomistic", but Robert Klein Engler is and he reports:

...CNN.com reports that "Even Cardinal Norberto Rivera Carrera, the archbishop of Mexico City, criticized U. S. immigration policy as ridiculous and defended Fox's comments ["the jobs that even blacks won't do"], saying: "The declaration had nothing to do with racism. It is a reality in the United States that anyone can prove."

That's not the whole of Cardinal Carrera's comments about immigration. He also has criticized the United States for "xenophobic attitudes" toward Mexican immigrants, calling it inconsistent to promote international free trade but refuse to let people cross the border for the basic human right to work. "Just as the borders are open to merchandise, that is all the more reason that the borders should be open to the human being," said the Cardinal.

Why is the archbishop of Mexico City getting involved in the illegal immigration dispute between Mexico and the United States and defending President Fox and his remarks?

...Cardinal Carrera should be reminded that it is a principle of Thomistic theology that both the family and the state are natural and necessary for our earthly happiness. Respect for the family means respect for marriage and respect for the state means respect for its laws and borders. Furthermore, respect for the culture of indigenous peoples is no different from respect for the unique culture of those living in the United States. It is hard to imagine how following Thomistic theology we can justify illegal immigration or in the Cardinal's words, "that the borders should be open..."

Although Cardinal Carrera is in favor of national unity when it comes to things Mexican, he seems not to be in favor of national unity when it comes to the U. S. protecting its borders. During the 1995 rebellion in Chiapas he made a plea for national unity and worried that Mexico might run the risk of coming apart. But when the U. S. decides on the national unity that comes with the enforcement of its immigration laws, he opposes such an effort...

See also "Can I blame the Catholic Church then?" about a logic-free Open Borders editorial from Cardinal Roger Mahoney.