Mexican drug cartels are responsible for trafficking fentanyl and other drugs that contribute to tens of thousands of American deaths every year. Because these organizations operate across borders and threaten U.S. public safety, waiting for formal permission could allow the crisis to worsen. While respecting Mexico's sovereignty is important, the United States has a responsibility to protect its citizens and should be prepared to take strong action, preferably in cooperation with Mexico but, if necessary, independently to address a growing national security threat.