Garry Dolley has developed a Ruby module called "Immutable" (Github repository). It allows you to make your methods immutable. As Gary says, "provide it a list of methods you don’t want touched and it’ll make sure they can’t be redefined." Effectively, it's a smack-down against monkeypatching.

Gary developed immutable to ensure that ActiveSupport wouldn't interfere with his attempts to improve Rails' loading time by reimplementing some ActiveSupport methods in C (by redefining his own changes).