No special international court exists for international environmental affairs, so states and other actors address transboundary issues in international and regional courts (ICs), leading to challenges via various fora and strategies. In the absence of a specialist court, ICs try different avenues to achieve desired outcomes, with constructive effects. They may be asked to handle similar environmental legal questions, leading to more diverse judicial practice. Those addressing similar issues refer to each others' judgments, to counter the fragmented structure of international law and lead to more consistency. ICs' diverse approach to such claims should be seen as an advantage rather than a constraint. There are also challenges. In the absence of an international environmental court, disputes are addressed by ICs with general jurisdiction (ICJ) or with specific non-environmental competence (WTO Dispute Settlement Body or regional human rights courts). Environmental legal issues arise before ICs as either justified exceptions or extensions of legal rights and obligations, not as the basis of claims. Such legitimacy questions are addressed in the six parts of the book.