While this is an unfortunate incident, it is not the first time these things have happened-- only the first time a chapter has been held responsible.
The Greek system is a tad different here than in other places. First off, it is highly unfavored by the university and most of it's students. Housing, like AOPirose mentioned is rented to the fraternities and sororities by the University, and University rules are the ones that are followed (the Intersorority Council rules are a tad looser than most national ones concerning alcohol to accommodate Stanford dorm traditions).
As for the punishment, sororities can sponsor events that involve alcohol, as long as there is a third party vendor to accept legal responsibility for checking identification and serving drinks to only those who are over 21. Those are the University’s rules in regard to sororities, set to reflect the Panhellenic agreement on alcohol policy set a few years back. Alcohol probation is a serious matter.
I am very gald they did not lose their charter. It would have been very sad to see them go after a stunt by so few!
What upsets me the most is the lack of punishment for the football players involved. One of our chapter membmers wrote a very good editorial on that which you may read here:
http://daily.stanford.edu/tempo?page...=0001_article.