
Two safeguards:

1. The FBI could be asked to produce the law enforcement block to the escrow
agencies, and associate it with a particular court order;

2. If the thing comes to trial the defense attorneys can probe this issue
closely. It is not too different from proving that the speaker on a legal
wiretap is the person the court order covered.

Putting it another way, this question is not very different from the
pre-clipper question "What's to prevent the FBI from getting a court order
to tap Al Capone and then using it to tap Jonathan Livingstone Seagull
instead?"

David