>>In Canada we currently have a serious problem with U.S. imposition of duties on softwood lumber, where they use both the "Free Trade Agreement" and GATT in an attempt to impose their will on Canada.
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>So it seems that some sort of international court is needed not only for criminal prosecution, but to settle other issues as well.

Oh it's already there and "working" - GATT. Trouble is, it has the identical problem of intruding on sovereignty. In this case it is not related to criminality.
As I observe it, another flaw in its workings is that issues take a long time to be 'resolved' and it is that time gap that is effectively used to achieve the end desired by the offending country.
For example, the U.S. can expect such hardship in Canada's lumber industry that we will cave in. This will gie them what they want and they will then drop their complaints to the international bodies.