Sorry, I'm not familiar with Freenet. Why must you use Tor to browse it?
In recent years, investigators have been using customized clients to serve child porn, and track which peers receive it from them. For IPs in their jurisdiction, they get and execute search warrants.
Although there is arguably plausible deniability, most defendants lack the will and resources to fight. So they typically plea bargain.
Anyway, if you use Tor, they can't find you. But it's not as simple as that, really. Basically, you lease a VPS, working ~anonymously via Tor. You run a Freenet node on the VPS, and access the webGUI as a Tor onion service. They can take down the VPS, if they like, but won't know who was using it.
Traffic is not just obfuscated, it is encrypted. Sure, you see the IP of a peer which transfers stuff across your client - but you do not know what the stuff is as it is encrypted.
So the IP address is worthless unless you figure out a way to guess what the stuff is, and who requested is.
See my other reply in this thread for further details.
As far as "who requested" the stuff, as you say in your other reply, they have some statistical arguments. I agree with the Freenet Project that they're very likely bullshit.
However, if you're facing criminal charges, you'd better have resources for expert testimony to discredit their arguments. And if you don't, accepting a plea bargain may be the best option. Even if you are truly innocent.
But generally, I'd rather avoid having a warrant served, and my stuff impounded. So advertising my IP address as a Freenet node seems like a dumb move.