The Price Of Freedom — E.C. Tubb

When his wife is murdered, victim of an assassin's bullet, businessman Dell Weston finds his life falling apart. Betrayed by his partner, he loses control of his company, and descends into the lower strata of a dog-eat dog society. Somehow, Dell manages to survive long enough to question the very fabric of civilization, and the role played by the mysterious figures in grey - the Arbitrators.