"That [The Elements of Law] was a polemically pro-royalist work was obvious; as Hobbes plainly stated in one of its final chapters, the idea that subjects could maintain rights of private property against the sovereign was a claim that he had 'confuted, by proving the absoluteness of the sovereignty.' But The Elements of Law was no mere polemical pamphlet. In it Hobbes had attempted to base his political principles on an account of human psychology that was compatible with (although not necessarily dependent on) his mechanistic physics. The reduction of 'reason' to instrumental reasoning was an important part of this psychological picture. Reason, on this view of things, did not intuit values, but found the means to ends that were posited by desire; desires might be various, but reason could also discover general truths about how to achieve the conditions (above all, the absence of anarchic violence) in which desires were least liable to be frustrated. By defining that which is 'not against reason' as 'right,' Hobbes also made the transition to a different type of general truths: definitional truths about rights and obligations, which would make the claims of the anti-royalist politicians as necessarily false as those of incompetent geometers. For sovereignty to exist at all, Hobbes argued, it was necessary for all the rights of the subjects to be yielded to it; what he tried to show was that the reasons that made sovereignty necessary also made it absolute..." - Noel Malcolm, "A summary biography of Hobbes," from The Cambridge Companion to Hobbes, pp. 28-29, (emphases my own)
Malcolm doesn't get it quite right. He claims that Hobbes's The Elements of Law was "no mere polemical pamphlet." The right approach would be to say that "It is and it isn't." It is because he uses exclusionary definitions to define his opponents right out of existence (that's why he wrote it). And it isn't because, yes, it also provided a venue for Hobbes to explore his own theories about psychology and the state as founded on his (anti)metaphysical position. In short, by establishing his definitions on the basis of an uncontested "fact" (namely, that sovereignty should exist, something that no politico in the 1600s would've contested), Hobbes concludes that the natural conclusion to accepting that "fact" is his (pro-royalist) conclusion. It would be misleading for me to claim that Hobbes is doing anything new here because he's just walking down old rhetorical highways. It's perhaps summed up best by Edward Markham's old poem "Outwitted": "He drew a circle that shut me out / Heretic, rebel, a thing to flout / But love and I had the wit to win; / We drew a circle that took him in."
If I have time I'll find the passage from The Elements of Law and explicate it at length.