Tom Ginsburg (international and comparative law, Asian law, law and development) at the University of Illinois has accepted a senior offer from the University of Chicago. As part of a big push in the international law area, Chicago has also added this year at the junior level Anu Bradford (international trade), a Finnish lawyer finishing her SJD at Harvard who was being widely recruited by other top law schools; and also Daniel Abebe (public international law, foreign relations law), who is presently a Bigelow Fellow at Chicago, where he is finishing a PhD in political science.
I should add that it is a real testament to Illinois's eye for faculty talent that Ginsburg is the third 'rising star' Chicago has recruited from there in the last couple of years; the other two were Lee Anne Fennell (property, land use, behavioral law & economics) and Richard McAdams (criminal law, law & social norms). Illinois has also, it should be noted, warded off some attempted raids on its strong faculty from other top law schools in the last few years.
UPDATE: Add one more to Chicago's big push in international and comparative law: Rosalind Dixon, whose areas include comparative constitutional law and international human rights, has also accepted an offer to join the Chicago faculty.