That could become a loaded policy, one which encourages universities to crank out graduates with those degrees, not necessarily with the expected understanding. [1]

I'm not saying its a bad idea, but it draws a somewhat arbitrary line in the sand, one which would eliminate some of the "desirable" immigrants - entrepreneurs that have dropped out and gone on to build amazing companies.

[1] A good example can be found here: http://v.cx/2010/04/feynman-brazil-education and the associated discussion http://news.ycombinator.com/item?id=2483976