International investment law as a legal system, is known as a subsidiary or specialized system of public international law. Regardless of the nature of this legal system, its norms and rules have been applied to governments and investors (both natural and legal persons) for many years. The main objective of this research is to provide a suitable model and solutions for solving possible problems in the field of legal mechanisms for securing foreign investment in international law. The present study is a documentary and evidence-based descriptive study derived from the study of documents, books, laws and regulations, articles and the Internet, and library data collection tool was used. The findings of the research indicate that domestic law is the most important source of international investment law, and other subsidiary sources actually play a complementary role for domestic laws of countries. The prohibition of double taxation, prohibition of expropriation, insurance establishment, freedom of trade, acceptance of the international responsibility of the host state and payment of compensation, can be considered as legal strategies to protect foreign investors' ownership in the international trading system.