The opinions in the headquarters were more and more inclined towards quick proceedings to avoid increase in the number of prisoners. To speed up the process, the Commander-in-Chief proposed the establishment of field courts martial to the Senate. The general idea was that the worst criminals were to be tried in field courts martial and the big crowds allowed to leave for home. Mannerheim was "inclined to release those red prisoners who were given good recommendations from their home regions, and particularly those who could be considered to have been forced to take part in the uprising". This proposal had practical grounds too. The troops were needed on the front, and there were not enough men available to guard the prisoners. On the other hand, Mannerheim was already thinking of Finland’s ability to unite: the best strategic frontier of a state lies in its unity. He emphasized the importance of building a bridge between the different sections of the post-war nation.

Mannerheim managed to persuade Karl Söderholm, the highest judicial dignitary of white Finland, the president of Vaasa Court of Appeal, to his idea of setting up field courts martial by interpreting military criminal law and regarding the country as being in a state of war. The lawyer members of the Vaasa government, however, took a different viewpoint. In regard to the legislation in force, these field courts martial could not be set up. War against Russia could not have been declared, as the parliament had not been assembled, and the law did not know of such a thing as a state of war during a civil war.

The starting point of the Vaasa Senate was the principle that the rebels were to be tried and convicted on the basis of the general criminal law, and, in case of political crime, in Courts of Appeal. For practical reasons, owing to the large number of prisoners, a decision was reached, however, to establish special Political Offence Courts. Judging the red prisoners was, as regards the whole of the nation, such an important procedure that it should take place in accordance with legislation in as normal court proceedings as possible. The Senate was afraid, and not without reason, that the pressing conditions would lead to illegal executions, if the trials were not organized rapidly. The so-called white terrorism had already begun.

As the police authorities of the headquarters proposed rapid trials Mannerheim said, "Enough blood has been shed. I do not want Finland to be called an executioner." The security chief of the occupied areas, Walden, put forward a proposition to the government on 8 May that field courts martial be set up and prisoners set free, but the government held to the view of investigations and sentences strictly according to the law. The law on Political Offence Courts was ratified in late May. The grounds for punishment were the regulations concerning treason in the criminal law, and in cases of leaders those concerning high treason.