It's a bit like the government using a whiteboard to track terrorists and the court has asked them to preserve what's on the whiteboard. The government consider

It's a bit like the government using a whiteboard to track terrorists and the court has asked them to preserve what's on the whiteboard. The government considers this too burdensome because if they can't erase the whiteboard they have to stop all tracking of terrorists. Unfortunately, scientists are still working on the ability to copy information. Perhaps some day they'll crack it.