Why did the Netherlands abolish its patent system in 1869? I answer this question by focusing on the implementation of the patent law from 1817. This unique patent system allowed the Dutch state to decide on the patent grant, length, costs and the imposition of other conditions on a case-by-case basis. I analyse the implementation of the law through an in-depth study of the patent dossiers and a comparison with Belgium, which shared the same patent law during and after its brief 15-year political union with the Netherlands. I reveal how the Dutch patent system radically changed its character in the ten years after the split with Belgium in 1830: amongst others, it no longer stimulated domestic inventors, stopped the publication of patents, and no longer intervened in the patent length, while Belgium took a different path. I argue that the political importance and the resources allocated to the patent system strongly influenced its development.