In the 1970s, Kouwenhoven was sentenced to two years in prison in the United States after being caught in a Federal Bureau of Investigation sting operation along with his then business partner Peter Rombouts while attempting to sell 6 stolen artworks, including a Rembrandt.
Syrian-born Richard (Amar) Chichakli was the financial manager of Bout's arms operations.
[10][11][12] Kouwenhoven was arrested in the Netherlands on 18 March 2005 and stood trial at the Court of First Instance in The Hague, starting 24 April 2006, charged with arms smuggling and war crimes in Liberia in the 90s, for which the Dutch public prosecutors sought a 20-year jail sentence and a fine of €450,000.
[13] The Court of Appeal in The Hague acquitted him of all charges on 10 March 2008 and sharply criticized the work of the prosecution.
[5] On 21 April 2017, Kouwenhoven was convicted in absentia to a 19-year jail sentence for illegal arms trafficking and complicity in war crimes in Liberia and Guinea.