The value of the Open Skies treaty comes from nearly three decades of evidence-based assessments and significant normative endorsement. Our focus in this short piece is on implications for northern North America, and we offer a simple assessment with regard to the Arctic: the U.S. decision to withdraw from Open Skies significantly favours the Russian Federation. We outline three main reasons for this assessment: 1) degraded visibility of the so-called ‘Russian militarized Arctic’, and uncertainty about Russian defence capabilities along the Northern Sea Route; 2) impacts on deterrence and defence spending strategies, and 3) erosion of Arctic security cooperation and strategic stability.