Master of Life and Death — Robert Silverberg

By the 23rd century Earth's population had reached seven billion. Mankind was in danger of perishing for lack of elbow room--unless prompt measures were taken. Roy Walton had the power to enforce those measures. But though his job was in the service of humanity, he soon found himself the most hated man in the world. For it was his job to tell parents their children were unfit to live; he had to uproot people from their homes and send them to remote areas of the world. Now, threatened by mobs of outraged citizens, denounced and blackened by the press, Roy Walton had to make a decision: resign his post, or use his power to destroy his enemies and become a dictator in the hopes of saving humanity from its own folly. In other words, should he become the MASTER OF LIFE AND DEATH?