Either the data or system is secure, or it isn't. Technologically, if there is a way for a judge to authorize reading a single X; then it is a hole that eventually will allow to read all X without the warrant by others as well.
As an example, if a cellphone network software allows for FBI wiretaps, then that can be used also by illegal wiretapping (http://en.wikipedia.org/wiki/Greek_wiretapping_case_2004%E2%... - the criminals weren't even identified). And if a system is secure (for any reasonable definition of the word secure), then noone can break that security, no matter what warrants they have.
There is no middle way. If I'm allowed to protect my communications from random illegal snoopers (say, corporate espionage); then that protection will be just as effective against legal snoopers.