There are a couple of elements that are immediately glaring in terms of the question. The first is that I think you need to specify "the current issue." The Keystone Pipeline is a challenging element on many fronts that there are several "issues" with it. I am not sure there is one "current issue." For example, are we examining the economic issues with it? Is "the current issue" whether or not the pipeline will actually help with oil consumption? Is the issue that needs to be solved the environmental impact of it? There are many concerns with it, and I think that more here is needed.
I do not think that international law will have much to say about the Keystone Pipeline. Nations are free to make agreements with one another relating to commerce and domestic issues such as energy production. Should International Law speak to the Keystone Pipeline, I think that Pandora's Box opens in that so many other issues around the world will become subject to International Law. For example, I would say that the crisis in Syria is more deserving of International Law concerns and enforcement more than the Keystone Pipeline. The other issue here is that I think that more detail is needed on where the need for International Law exists in the Pipeline. Does International Law need to speak for the element of environmental concerns? If so, then would it not need to speak for the same concerns around the world? Again, I think that there is a need for greater specificity in the question.