Hutton the sealer

I can understand Lord Hutton sealing - for 70 years!!! - the evidence before him consisting of Dr Kelly's medical records. After all, Hutton doesn't want them to come out, as he would end up looking either incompetent or completely crooked, or (probably) both. What I don't understand is how his sealing ability can possibly extend beyond the evidence before him. How does he seal materials which are otherwise available? This is starting to look like some kind of attempted legal trick:

"Last night, the Ministry of Justice was unable to explain the legal basis for Lord Hutton’s order."