The historic summit between U.S. President Donald Trump and North Korean leader Kim Jong Un ended with the celebratory signing of a declaration that the United States and North Korea will “work toward complete denuclearization of the Korean Peninsula.” But the declaration, which echoes the vague language of an April joint statement by Kim and South Korean President Moon Jae-in, does not commit North Korea to a firm, verifiable process for giving up its nuclear weapons or the associated research-and-development effort.