All of the BU career guides are including in this link. Below are the 2 career guides that are particularly helpful for international law careers.
Also, some international law jobs get posted on the BU symplicity.
American Society of International Law (ASIL) is the main hub of international legal debate, exchange, cooperation etc. They have advisory boards on all kinds of international law issues, including human rights, international criminal law, environmental law, law of armed conflict, and international economic law. They have publications, education resources, and job postings.
PSJD: This is a major job and employer database for public interest positions, including public interest nonprofit and law firms, prosecution and criminal defense, the judiciary, and government positions. You can filter by legal area, strategies (litigation, clinical, policy etc.), experience, salary etc. If you want to find international positions, you can control by location (type in the Hague, Strasbourg, Brussels etc.)
NALP: This is a major legal career database for all kinds of jobs. You can also find corporate positions in international law (just control for international law as practice area). You can also find private law firms that especially focus on international law ahead of OCI and submit applications to those firms.
New York Law School Center for International Law – Career Resources (Perhaps the best list for organizations and links)
Harvard Law School Guide: This links to HLS's "Career and Application Guides," and has subject matter guides (e.g., "Human Trafficking" or "National Security") and also find "Cheap Living Guides" for finding affordable housing in different cities (mainly U.S., but some international).
Find international lawyers and law firms across the globe
State Department List of NGO and International Organizations in Global Criminal Justice