Nope. He said he was surprised it could be so spectacular.
So, as he had tried years before 9/11 to blow the towers, you think he said "yes it's me", but he didn't.
Either, he didn't say no, for US were advertising for Al Qaeda (prestige for his anti-america recruitment).
He was, but not for 9/11 attacks. That's your legal link, but it's not enough to be an evidence.
Knowing who really is the offender.
Innocence presumption.
There were many evidences that the japanese were the attackers of Pearl Harbour. They had been clearly identified.
I try not to defend Ben Laden, but truth is the best for justice and peace.