Foreign Operator of Obscene Internet sites Pleads Guilty of Obscenity Charges and Foreign Operator of Obscene Web pages Arrested on Federal Obscenity Charges]. They went after Croce for videos with "bukkake, fisting, and depictions of defecation, urination, and vomiting along side sex acts."
Croce was the producer who created "2 Girls, 1 Cup" -- which means that the recognition/mainstream awareness of the actual video had too much to do with the prosecution,
https://thepornscat.com/ fairly than a particular crackdown on scat porn. Note that additionally seems to comply with a 2004 "pornography crackdown" by the Bush administration. (Remember, they're the knuckleheads that additionally put Chong in jail for promoting bongs, so...)
Also good reading, on the Volokh Conspiracy from 2012 a couple of plank within the GOP platform about "Current Laws on All Forms of Pornography and Obscenity Must be Vigorously Enforced."
I'm not a lawyer, and definitely not your pal's lawyer, however here's what I'd tell them -- evidence of prosecution of possession of "scat porn" in as we speak's society is passingly uncommon, and barring a significant sea change in priorities, they're unlikely to be focused just for watching scat porn. It's barely more possible they may very well be charged in the event that they were producing some form of porn, however just watching it? Not a lot.