I agree with you that the wording is a bit awkward. I think that if we were to look at "claim" in chapter 17 as representing what needs are present, I would say that a significant claim would be the need for social solidarity. Chapter 17 is a significant moment in the book in that Steinbeck is able to show the migrants as not people who were completely driven by self interest, solely. Rather, they are shown to be individuals who accept the need for rules and structure in order to forge social solidarity with one another. The fundamental "claim" that is present in chapter 17 is how individuals who have been displaced from their communities and social settings will be able to form these elements in the new conditions of migration and the sense of impermanence. The "claim" is this desire for permanence and solidarity in a world of contingency and fragmentation. The "claim" is the idea that lawlessness does not benefit anyone and that this community established is one where the interests of all are protected if each person's interest is represented. In my mind, this is the "claim" that emerges from this chapter.