In the first session, which lasted from 29 May to 1 June, he expressed support for the future of Indonesia to be a strong unitary state, arguing that it was by Indonesian societal norms.

During the BPUPK recess, this was subsequently incorporated into a preamble for the future constitution, the Jakarta Charter by a Committee of Nine, which did not include Soepomo.

[6] When the BPUPK reconvened for its second session, which began on 10 July, a 19-member committee was set up to produce a draft constitution, and Soepomo played the dominant role in its deliberations, which took place over three days.

He deliberately produced a constitution that had a strong central government with power concentrated with the president, and without a clear system of checks and balances, in line with his opinions.

Specifically, he supported integralist totalitarianism based on the family ideology and proposed the Indonesian state be modelled on Nazi Germany and Imperial Japan.

In the discussions, he was strongly opposed by Mohammad Yamin, who called for a more Western-style democracy with guarantees for human rights.

[12] After his terms as Minister of Justice, Soepomo became a lecturer at Gadjah Mada University,[5] as well as the Jakarta Police Academy.