Currently, Boo allows for events to be raised outside of the assembly they have been declared in. This raises security issues for those wishing to use an event-based environment with CAS. The follow code sample should not work and demonstrates the problem by invoking TriggerMe outside of its declaring assembly: """External assembly.""" namespace BooEventlib import System class MyClass: def constructor(): pass event TriggerMe as callable() """Consuming assembly.""" namespace BooTesta import System import System.Drawing import System.Windows.Forms import BooEventlib m = MyClass() m.TriggerMe += { print "LOL!" } m.TriggerMe() //Should not be possible.