 It is generally thought to follow that child pornography, which is taken to involve the actual sexual abuse or exploitation of children (with or without their apparent consent), can legitimately be banned in order to protect the interests of children, who are not yet competent to fully understand the nature of the choice they are making or to grasp the impact of their decisions on their present and future interests. For the same reason, liberals think that children can quite rightly be prevented by parents or by the state from purchasing or viewing pornography if this is thought likely to harm them. That child pornography should be banned is common ground between liberals and conservatives. However, pornography that involves the simulated abuse of children (for example, virtual child pornography, or consenting adult actors dressed up as schoolgirls) cannot legitimately be prohibited under the harm principle unless there is good evidence to suggest that consumption of this material causes significant harm to people other than those consenting adults involved in its production and consumption, for example, by causing those who consume it to abuse children or by eroticizing inequality. The U.S. Supreme Court has ruled that virtual child pornography is protected speech, partly on the basis that virtual child pornography does not harm actual children (Levy 2002).