A person’s tier level does NOT have any effect on whether the person is subject to the 2,000 ft law, how long they are required to register, or any other element of sex offender registration.
It is used ONLY to determine how often the person must update registration information.
The OPA, broadly, does not criminalise any specific words or depictions.
Rather, it leaves it up to a jury to decide what will tend to "deprave or corrupt" - which over the years has meant NOT finding obscene Lady Chatterley's Lover, the infamous "Schoolkids" issue of Oz, Inside Linda Lovelace and, most recently, during the case of Michael Peacock, full-hand fisting, urination, staged kidnapping and rape.
Defenders of the court ruling would argue that there was nothing defensible about the content of the chat logs, which pertained to “explicit conversation concerning incestuous, sadistic paedophil[ic] sex acts on young and very young children".