Of course what Giuliani obtained cannot be used for prosecution. The point is that access to evidence that could be used to prosecute was successfully blocked - and may still be.
You asked for proof that such access was blocked and I provided that. Perhaps AG Barr or an assistant was able, under some legal umbrella, to travel to Ukraine and obtain permissible legal evidence against the Biden's and ??.
I’m sorry I didn’t see or grok the part about the evidence that Giuliani obtained could not be used for prosecution. I remember when he was tweeting about this evidence. Why can’t it be used? Chain of custody? Now some memory is stirring in my feeble brainpan, about Barr and some others travelling to Italy and maybe another country more than a year ago IIRC.
Do you remember the details, or someone?