What, a judge tries the President?

Of course. This is why it is important for power in the State to be divided up: the government (executive) should be separated from the parliament (legislature) which, in turn, should be separated from the courts (judiciary) so that power is not concentrated in any person or body and everyone is subject to the law. This is a cornerstone of the democratic process.

But where this separation of powers does not exist, who tries the State?

At present, there is no means of enforcing international law through a legal process. The United Nations can impose, through the General Assembly, economic sanctions on a country, but short of armed intervention in certain circumstances we shall go into later, there is not a great deal that can be done.

So what's the point? I'm told I have these rights but what use are they if I cannot enforce them — if my government can abuse them with impunity?

Slowly but surely governments are becoming aware of the importance of a good human rights record. A poor human rights record is highly embarrassing to governments. It is bad for the image of the country; it is bad for business. They are able to get away with it partly because people do not know their rights in law. For this reason, the slogan of the World Conference in Vienna was: Human rights: know them, demand them, defend them.