The panelists are:
Luzius Wasescha, Elizabeth Chelliah, and Patricia Holmes.
Wasescha, a familiar name to many who follow this blog, is a senior Swiss trade official, who has held numerous important positions and served on several WTO panels. He has an academic training in law and (some years ago) wrote a book on the European Social Charter. Chelliah is a Singapore trade official who has also served on panels before, including one on US rules of origin where the concept of non-discrimination was interpreted in a circumscribed manner that is respectful of domestic sovereignty. Holmes is currently serving as Australia's ambassador to Argentina. She has a training in law, which apparently includes an advanced degree in international environmental law from ANU. A preliminary Google search indicates that she has been involved over the years in a number of policy processes and exercises related to trade and environment issues.
Over the next days and weeks, those interested in this dispute will doubtless be finding out more about the panel rulings, activities and publications of these individuals. Stay tuned.