In a co-written letter for the Guardian, Professor Penny Green denounced Spain’s attempts to block the referendum in Catalonia: “We support the demands by constitutional lawyers in Catalonia and Spain to cease all action disrupting the referendum there. Section 155 of the Spanish constitution states that the government can only compel an autonomous community (state or regional government) to carry out legal actions with the prior consent of a majority of the Spanish senate. No such vote has taken place.”