For his doctorate in 1823 he produced a thesis entitled De jure et natura legitimae secundum jus civile et hodiernum (Luik, Collardin, 1823).
This brochure went down badly with the Minister of Justice and the ministry began to put Tielemans' correspondence with De Potter under surveillance.
On receiving a letter informing him of the Belgian Revolution, he returned to Brussels and on 6 October 1830 the Provisional Government appointed him a member of the Constitutional Committee and Administrator-General (effectively minister) of the Interior.
He was very busy in the second of these roles - he had to organise the administration, national, provincial and municipal elections, schools, public works and measures regarding trade, agriculture and industry, among others.
In the sitting of the National Congress of Belgium on 9 December 1830 he released a report[1] reflecting the difficulties he had encountered and the seriousness and complexity of the situation as it had materialized.
From 26 February to 23 March 1831 he was minister of the interior in the first cabinet under regent Erasme Louis Surlet de Chokier, but he was dismissed after only one month.
Minister of Justice Joseph Raikem alleged this had been a mistake, but in the meantime a new governor of Liège had been appointed so Tielemans could not return to this post.