ASACP has released a self-labelling tag at:
http://www.rtalabel.org/
labelling laws are not that far from being on the books. You can use ICRA, but it is more involved.
ASACP's RTA label is just saying the content is restricted to adults, no classifications other than the binary bit of for adults only.
I strongly encourage websites, especially affiliates, to use the ASACP RTA label.
Fight the PSA!