At various times after 1922, Mussolini personally took over the ministries of the interior, foreign affairs, colonies, corporations, defense, and public works. Sometimes he held as many as seven departments simultaneously, as well as the premiership. He was also head of the all-powerful Fascist Party and the armed local fascist militia, the MVSN or "Blackshirts", who terrorised incipient resistances in the cities and provinces. He would later form the OVRA, an institutionalised secret police that carried official state support. In this way he succeeded in keeping power in his own hands and preventing the emergence of any rival.

Between 1925 and 1927, Mussolini progressively dismantled virtually all constitutional and conventional restraints on his power, thereby building a police state. A law passed on Christmas Eve 1925 changed Mussolini's formal title from "president of the Council of Ministers" to "head of the government". He was no longer responsible to Parliament and could only be removed by the king. While the Italian constitution stated that ministers were only responsible to the sovereign, in practice it had become all but impossible to govern against the express will of Parliament. The Christmas Eve law ended this practice, and also made Mussolini the only person competent to determine the body's agenda. Local autonomy was abolished, and podestàsappointed by the Italian Senate replaced elected mayors and councils.

All other parties were outlawed in 1928, though in practice Italy had been a one-party state since Mussolini's 1925 speech. In the same year, an electoral law abolished parliamentary elections. Instead, the Grand Council of Fascism selected a single list of candidates to be approved by plebiscite. The Grand Council had been created five years earlier as a party body but was "constitutionalised" and became the highest constitutional authority in the state. On paper, the Grand Council had the power to recommend Mussolini's removal from office, and was thus theoretically the only check on his power. Only Mussolini could summon the Grand Council and determine its agenda. To gain control of the South, especially Sicily, he appointed Cesare Mori as a Prefect of the city of Palermo, with the charge of eradicating the Mafia at any price. In the telegram, Mussolini wrote to Mori:

"Your Excellency has carte blanche; the authority of the State must absolutely, I repeat absolutely, be re-established in Sicily. If the laws still in force hinder you, this will be no problem, as we will draw up new laws."^[64]

He did not hesitate laying siege to towns, using torture, and holding women and children as hostages to oblige suspects to give themselves up. These harsh methods earned him the nickname of "Iron Prefect". In 1927 Mori's inquiries brought evidence of collusion between the Mafiaand the Fascist establishment, and he was dismissed for length of service in 1929. Mussolini nominated Mori as a senator, and fascistpropaganda claimed that the Mafia had been defeated.^{[citation needed]}