Thanks for the details! Indeed I hadn't realized that the Pirate Bay trial convictions were based specifically on Swedish law. I figured that international treaties had been involved somehow. Though of course, you've hit the nail on the head: the laws are so similar, and with outcomes so similar, that all copyright law might as well be emulating U.S. policy, even if there are subtle differences in implementations.
International Treaties are... weird. Generally (very very generally), they are agreements between governments to take certain actions, possibly with penalties if such actions aren't taken.
The penalties would tend to be trade or economic sanctions from the other signatories.
The actions to be taken usually involve creating national legislation that implement this framework [See for example the UK's Human Rights Act implementing the European Convention of Human Rights]. Broadly, once national legislation has been created, then national courts can enforce it [Until the HRA was created in the UK, UK Courts couldn't hear EConvHR cases as they can only look at national law due to Parliamentary Sovereignty]. Think of it as being similar to how US Federal Courts have jurisdiction over Federal Crimes, and US State Courts have jurisdiction over State Crimes.
This means that an international treaty can be dead in the water despite being signed, should the national government not be able to get the implementing legislation passed - think of how ACTA was signed by the EU (and member states), but rejected by EU Parliament (and some member states parliaments).
This is why it was newsworthy when the US President tried to claim that having been signed by the US obliged the US to implement it via an executive order, bypassing the democratic congress (and thus, in a way, weakening the concept of national sovereignty).
But yes, copyright laws are broadly similar - mostly because the Berne Convention is widely accepted and implemented on a national level (along with organisations such as WIPO). An example of where the subtle changes come from is because the BC specifies that exceptions can be made for "fair" use, but doesn't explicitly define what "fair" use is. Another example is the "rule of the shorter term" - when a work is published abroad as well as at home, the author only gets the shorter of the two protections, but not all signatories have implemented this. Interestingly the US was relatively late in signing and implementing the BC.
Disclaimer: I am not a copyright lawyer. I am not a lawyer in any way. But I do have a keen interest in the law, and consider myself relatively well informed in such areas.
