Judicial Decisions

European Court of Human Rights - Advisory Opinions
Access to advisory opinions
European Court of Human Rights - HUDOC database
Use the advanced link in the top-right corner to find cases that reference a particular article of the European Convention on Human Rights.
European Court of Justice Website - CURIA
The "cases" tab offers a search form to find cases using many different field searches.
International Court of Justice Website
The ICJ website provides all documents filed in (and issued by) the Court re: contentious cases and advisory opinions. Search function is a bit limited, though.
Oxford Reports on International Law
This database allows you to search by keyword and/or subject across different courts/jurisdictions. Link for an advanced search is in upper-right corner.

Jurisprudence from other Tribunals

UN Treaty Bodies - Jurisprudence Database
Find jurisprudence emanating from the United Nations Treaty Bodies which receive and consider complaints from individuals: the Human Rights Committee (CCPR), the Committee against Torture (CAT), the Committee on the Elimination of Discrimination against Women (CEDAW), the Committee on the Elimination of Racial Discrimination (CERD), the Committee on the Rights of Persons with Disabilities (CRPD), the Committee on Enforced Disappearances (CED), the Committee on Economic, Social and Cultural Rights (CESCR), and the Committee on the Rights of the Child (CRC).
World Trade Organization - Disputes by Agreement
Find documents related to disputes at the WTO