The Law Lords merely decided that it was lawful for the SFO to have dropped its inquiry into the £43bn deal with BAE Systems over 'fears' that it would threaten national security.
That is absolutely not the same thing as finding that BAE was innocent of accustions that it made illegal payments to Saudi officials.
Had the SFO inquiry continued, it could have provided the answer to such allegations. But Bliar leant on the SFO, so the truth will probably never be known - and suspicions will therefore remain.
The Law Lords decision does not, as I see it, prevent the SFO from re-opening its case, should it choose to do so.