The Democratic and Republican presidential contenders have begun defining their approach to major foreign policy issues as they jockey for position in their parties’ primaries.

Halfway through his term, President Andres Manuel Lopez Obrador is moving from bending democratic norms and laws to breaking them—a slide that the U.S. cannot afford to ignore.

The ICC appeals chamber’s decision to move ahead on an investigation of grave abuses by combatants in Afghanistan, including U.S. forces, marks an unprecedented move that is likely to arouse intensiv…