There are a number of resources available through the HeinOnline database which contain international content.
Index to Foreign Legal Periodicals is an index to journals which are international in scope. You can limit your search results to English language only. Journals that are available full text through HeinOnline will have a direct link.
Foreign & International Law Database is a collection of international tribunal/judicial decisions, international yearbooks, and U. S. Law Digests.
Hague Academy Collected Courses Online (Racueil des cours). The text of advanced educational courses which the Academy offers every summer on topics of public and private international law.
European Center for Minority Issues. The ECMI conducts practice-oriented research, provides information and documentation, and offers advisory services concerning minority-majority relations in Europe. This library contains several publications of the ECMI, including ECMI Reports and Working Papers.
History of International Law Includes more than 1,100 titles and 800,000 pages dating back to 1690 on International Law subjects such as War & Peace, the Nuremberg Trials, Law of the Sea, International Arbitration, Hague Conferences and Conventions.
International Law Association Reports. The International Law Association's objectives are the study, clarification and development of international law, both public and private, and the furtherance of international understanding and respect for international law. The International Law Association Reports of Conferences contain the International Committees' reports and a record of the discussions at the Conference working sessions, together with the adopted Resolutions.
U. S. Treaties and Agreements Library. This library includes all U.S. treaties, whether currently in-force, expired, or not-yet officially published. This is the world's largest and most complete online collection of U.S. treaties and agreements and includes such prominent collections as the United States Treaties and Other International Agreements set.
World Constitutions Illustrated. This library enables legal scholars to research the constitutional and political development of every country in the world. It includes the current constitution for every country in its original language format and an English translation, as well as substantial constitutional histories
WestlawNext. WestlawNext has a number of international materials available. Treaties, Court opinions, and European Union materials may be found.
LexisAdvance. Lexis does not appear to have migrated all of its international content to LexisAdvance. My recommendation is to search the lexis.com database and under the "Area of Law - by Topic" select "International Law."