J. Benton Heath introduced the topic. Essential security interests clauses have been invoked in a handful of cases, including several cases arising out of the Argentine debt crisis and the twin cases brought by Deutsche Bank and CC/Devas against India relating to satellite frequencies, with mixed outcomes and reasoning. In several treaties, these clauses also refer to public health measures, but there is little guidance on how such clauses should be interpreted or applied. Using a fictional but realistic scenario, the advocates and tribunal members—playing assigned roles—were asked to consider whether public health exceptions are self-judging, whether they deprive a tribunal of jurisdiction or go to the merits, and what showing is required for the clause to apply. The scenario also raised broader doctrinal questions about the nature of exceptions in investment treaties, their relationship with the treaty's primary obligations, and the interrelationship between security clauses and the customary international law defense of necessity.