The chief political incident of his rule was a decree abolishing slavery in 1854.
His action in abolishing all tolls established on the Rhine since 1250, led to the formation of a league against him by the Rhenish archbishops and the count palatine of the Rhine; but aided by the towns, he soon crushed the rising.
From early youth he took a prominent part in the politics of his clan, and owing to his extreme opinions with regard to the expediency of abolishing the Tokugawa administration, he was banished (1858) to the island of Oshima (Satsuma), where he attempted unsuccessfully to commit suicide.
In the debate abolishing the court of wards he spoke, like most landed proprietors, in favour of laying the burden on the excise instead of on the land, and on the question of the restoration of the bishops carried in the interests of the court an adjournment of the debate for three months.
From a party-political point of view the period of Sir Henry Campbell-Bannerman's premiership was chiefly marked by the continued controversies remaining from the general election of 1906, - tariff reform and free trade, the South African question and the allied Liberal policy for abolishing Chinese labour, the administration of Ireland, and the amendment of the Education Act of 1902 so as to remove its supposed denominational character.