Complex sentence: The Lacedaemonians had appealed to the Roman senate about the possession of some disputed land, and had received for answer that the decision of all causes, except those of life and death, rested with the great council of the Achaeans.
Split into simpler sentences: The Lacedaemonians had appealed to the Roman senate over the possession of some disputed land. In response, the Roman senate had said that decisions on all causes, except those of life and death, rested with the great council of the Achaeans.