In principle, only the emperor had authority, but in fact, the emperor basically did not exercise powers by himself, but a cabinet (prime minister) made decisions with the emperor's consent.
なお、天皇の権限といっても、運用上は天皇が単独で権限を行使する事はなく、内閣（内閣総理大臣）が天皇の了解を得て決断を下す状態が常であった。