In theory it's training assassins and having other Houses purchase them for use, we as a House are sort of a Patron in that manner.<br/><br/>A quick read-up on what defines Kanly is it is a formal fued and the rules only dictate no innocent bystanders are to be harmed in enacting it (thus 'No Atomics' as there's too much risk for collatoral damage and the Landsraad is a house of cards to start with).<br/><br/>Kanly comes from the fued passing from father to son and either ends when both bloodlines are dead or the two Houses make peace (In Dune, the Kanly between Atreides and Harkonnen ended with the destruction of the Harkonnens (The Baron is killed by Alia and Feyd falls to a duel with Paul - The Beast is assumed killed by the Fremen soon after the novel ends).<br/>This ended the Kanly though funnily enough Lady Jessica was the daughter of Baron Harkonnen, making Paul and Alia also have Harkonnen blood.<br/><br/>Assassins are used mainly as a quick and clean way to enact the fued as it's assumed that the assassin will<em>only</em>kill their assigned target.