The legal doctrine under which the MIT administration feels pruessure to do these things is called In Loco Parentis and its incarnation at MIT is particularly influenced by the death of Scott Krueger[1]. MIT has to at least appear[2] to be taking issues of student safety and the use of intoxicating substances seriously.

[1] http://news.mit.edu/1998/da-0923 [2] In the aftermath of a GHB overdose incident at Senior House's annual party Steer Roast in spring of 2008, there were rumblings that Steer Roast would be prohibited. I was part of a group working with the administration to allow Roast to continue. Rather than being just a CYA, The members of the administration whom I worked with appeared to genuinely and sincerely care about safety in this domain.