The site is a little unclear: it appears he wasn't prosecuted for the "2 girls" video, but rather "hours of videos in which females engaged in sex acts involving human waste and animals." [1] His Wikipedia page lists some of the titles that suggest that a horse (horses?) and dogs were involved, as well as "evidence suggesting Isaacs' provided controlled substances to the actresses in his films to compel them to perform." [2]
[1] http://www.dailymail.co.uk/news/article-2264024/Ira-Isaacs-F...