First of all, your friend made a really stupid 
move. It was ridiculous to trade a huge number of 
cels to someone for what is essentially a fansub. 
I hate to put it that way but that was dumb and I 
hope he learned a VERY good lesson from it so he 
doesn't make a bigger mistake later.

That said. . . . I think your friend needs to 
write back to Aaron and point out that it was 
*Aaron* who is the one trying to sell the fansubs 
on CD - he's trying to sell them to Eric for 40 
cels (which I'm assuming are legitamate cels and 
thus have a certain value). Thus it is Aaron who 
has ALREADY committed mail fraud, and Eric 
commits no fraud by returning what was sent to 
him. (Eric is in a grey zone here since he had to 
have known in the first place that these were not 
licenced copies he was trading for - however it's 
tough to commit mail fraud by returning something 
back to it's original sender.)

If Aaron insists that the CDs cannot be returned, 
I suggest that Eric pop off to the post office 
and mail them back to Aaron in such a way that 
Eric gets back paperwork verifying the package 
were received by the intended recipient. That 
means certified/registered mail for which Aaron 
himself will have to sign, with return receipt 
and tracking numbers and anything else that can 
put on it. He should then inform Aaron in a 
letter (if he can have the letter officially 
copied and sent registered as well, he should do 
so) that the CDs are unsatisfactory and that, 
according to their previous written agreement, he 
expects the return of his cels upon Aaron's 
receipt of the CDs in question or legal action 
will be taken.

After that point, if he's still having problems, 
you can get the postal service involved. . . But 
don't expect them to be incredibly helpful. More 
helpful might be contacting the police department 
local to Aaron's home address and trying to get 
them to help.

I wish Eric luck. . . He's going to need it.

Many Sharp Smiles,
--Drac