I'm going to comment on the question of whether copyright laws are in fact justified, rather than the question Bernard Gert addresses, namely, of whether it is morally wrong in general to violate laws (though in passing I can't stop myself observing that, when it comes to internet activities, it's not always obvious which country's laws should apply).

One possible view of copyright (and of intellectual property generally) is that the creators of such property have an absolute right of ownership, and that the job of the law is simply to protect this right.

But an alternative view is that intellectual property is a socio-legal construction (however it is with other forms of property) and that the job of the law is (a) to allow the public to maximally benefit from the creation, while at the same time (b) ensuring that there are sufficient incentives to encourage the creation in the first place.

Nearly all systems of modern law are based on the second view, as is shown by the fact that they place a time limit on the period for which creators can control their creations (twenty years for patents, seventy years after publication/creator's death for works of art, and so on).

From the perspective of this second view, it clearly makes sense that there should be some incentives for creators. But this leaves it open exactly how the balance should be struck between legal protection for creators and allowing the public to benefit. (This conflict is most obvious in the case of life-saving treatments patented by drug corporations, but the point is general.)

In practice, the legal balance is struck as a result of politic0-legal processes in which the creators' representatives argue for greater ownership rights, and and the consumers' representatives for more freedom.

In general, the creators' representatives invest vastly more resources in this process than the consumers' representatives. (Moreover, at an international level, the creators' countries generally have vastly more power that the consumers' countries.)

Given this, and applying Bernard Gert's test, it is hard to believe that any fully informed 'impartial rational' person would regard the current laws of intellectual property as justified.