overread: I'm a little confused - surely if the police have evidence to show that you might be hiding incriminating data within a hard-drive or a safe they have the right to appeal to a judge to gain the rights to entry to that disk/safe.
If in the case that you have locked/encrypted surely its normal procedure to require the person to then decrypt/unlock it without even needing further court action.
I guess I fail to see why this is such a major turning point ruling.
Sir, you clearely have no idea what you are talking about.
Self-incriminate is not only to tell judge "I did this" but also giving incriminating evidence. Of course police can take the drive, but they have to encrypt / unlock it by themselves.
This is how law works in countries that respect the rules.
overread: But surely if they've already got the court order to search your premises you have to let them in the house
First - you have to bear the Police actions, but you cannot be forced to actively do anything.
For example, you can't be forced to open the door, but you can't do anything if they will bust them up.
You are obliged only to be passive , not active.
For example, if they think you have drugs in a closet and say "open the closet, sir" you may say "GTFO, open it by yourself if you have a warrant".
They can't force you to do anything that may incriminate you.