see here

A local prosecutor with a thirst for headlines could certainly initiate a criminal charge against a website operator who fails to implement a viable form of age verification. While the courts may ultimately find constitutional problems with any given state statute, prevailing in court is never guaranteed. Moreover, as the United States Supreme Court appears to be swinging towards the conservative side, civil liberties cases will become more difficult to win. In addition to state law concerns, it should be noted that the Child Online Protection Act (COPA) requires age verification for adult websites. Commercial websites must implement age verification based on 1) credit cards; 2) verified passwords; or, 3) “other means” that are reasonably feasible under the current technology.[9] While the courts have thus far preliminarily enjoined COPA, [10] the case has still not been decided, and the law could still be upheld by the United States Supreme Court. The results of the pending Supreme Court nomination process may bear heavily on the outcome of this particular case when it reaches the High Court for the third time.Until then, webmasters cannot be assured that they are out of the woods with regard to COPA compliance. Moreover, the government has never promised that it will not retroactively enforce the Act against those webmasters who failed to comply while it was enjoined, assuming that the law is ultimately upheld. In sum, both state and federal law pose potential age verification concerns for adult webmasters. Moreover, as noted above, pending legislation may soon be adopted to require use of certain forms of approved age verification by adult webmasters.