How can Tuck's dean make Congress do anything? There is a strain of anti-immigration/xenophobia running through the U.S. right now. Post 9/11, it became more difficult to get a U.S. visa. I wouldn't be surprised at all if Congress has made it harder for internationals to get H1-B visas with unemployment as high as it is here in the States. Personally, I think the U.S. is shooting itself in the foot with these policies, but immigration is a contentious political topic these days.
As much as Tuck wants to make its program more international and attract quality international students, I can't imagine the school's dean would do anything to make it more difficult for applicants/students/graduates to get a visa.