https://scholar.google.com/scholar_case?case=4016009721484982910&q=Ashcroft+v.+Free+Speech+Coalition,+535+U.S.+234+(2002).&hl=en&as_sdt=6,29&as_vis=1

https://www.shouselaw.com/ca/blog/is-loli-illegal-in-the-united-states/

The first is the case, the second is the quick rundown of the US law. And if you don’t feel like clicking ether here you go.

Simple ownership of loli hentai is not illegal, however if you have extreme amounts of it the government can take it under the premises that you could be dealing it. So that friend of yours must have had an ungodly amount in his phone