Overriding a Rails default_scope
Solution 1:
In Rails 3:
foos = Foo.unscoped.where(:baz => baz)
Solution 2:
Short answer: Do not use default_scope unless you really have to. You'll probably be better off with named scopes. With that said, you can use with_exclusive_scope to override the default scope if you need to.
Have a look at this question for more details.