Stierneld appeared among the opposition to Gustavus III, King of Sweden in the Riksdag of 1786 and 1789, where he was one of the leaders of the nobility.

When the others arrested were released, however, he was detained because of his connections to the Russian ambassador, and was placed in the Varberg Fortress.

In 1790, he was released to marry his fiancée Charlotte Gyldenstolpe, a courtier of Hedwig Elisabeth Charlotte, Duchess of Holstein-Gottorp and a daughter of the king's favorite Nils Philip Gyldenstolpe; the connections of his spouse secured his rehabilitation, and he was appointed court chamberlain in 1792.

In 1821, he became one of the founders of the Royal Society for Publication of Manuscripts on Scandinavian History, in which he served as chairperson several times and also published several essays.

In this capacity, he forged, misquoted, manipulated and wrongly interpenetrated numerous historical documents to trace the genealogy of his own family to royalty and give his ancestors a more prominent place in history.