I am interested in obtaining an LL.M. in International Law. I have undergraduate experience in the field so I believe my chances of acceptance are good. Is their a "backdoor" to practice law if one has an LL.M and no undergraduate in law? Does anyone know any jurisdictions where LL.M. graduates may get called to the bar?

I would not think so, at least not in the US, the UK or Europe. The other thing is that you will need an undergraduate law degree in order to be accepted in the LLM programs (at least in most cases).