Concentration of power in the executive branch has fostered an American democracy increasingly prone to waging forever wars. Growing executive concentration and resulting executive unilateralism have been driven by a historical blend of personalities, domestic structure, changes in international regimes, and increasingly extreme legal theories. These theories of unilateral executive authority, espoused most aggressively during Donald Trump's presidencies, cannot be squared with the Constitution's vision that checks and balances do not stop at the water's edge. The tumultuous start of Trump's second term reveals that executive unilateralism has reached crisis proportions. A rule of law response will entail both short-term strategies of resistance and resilience and longer-term efforts at structural reform.