Though they are often lumped together, foreign law, international law and comparative law are all broad topics in their own right.
Foreign law involves the domestic laws of a foreign jurisdiction. International law has to do with the laws that regulate conduct between sovereign nations. Comparative law is the study of the differences between laws of various jurisdictions.
It is important to bear in mind that there may be a great many useful resources that will not be available in English.
See the first link for a guide to international law and the second for a guide to foreign law.