The Pakistani government is inching closer to a solution for one of its most enduring problems. On Jan. 6, Prime Minister Nawaz Sharif's administration announced that Pakistan's major political parties had all approved a measure, originally proposed in 2015, to join the historically autonomous Federally Administered Tribal Areas with neighboring Khyber-Pakhtunkhwa province. The merger is part of Islamabad's effort to promote development in the Federally Administered Tribal Areas -- Pakistan's poorest region -- and to strengthen local law enforcement to combat militancy there. The move would also free up military resources that Islamabad could then devote to its border with India, which has grown increasingly assertive in responding to cross-border attacks by Pakistan-based militants in the disputed territory of Kashmir. If successful, the merger would be among the most consequential reforms in Pakistan's nearly 70-year history. But though the initiative at last has the political support it needs to proceed,...