1) More a question for discussion - Horton's argument, from my quick first reading, appears to reject any principle from which political obligation arises, apart from continuing the existence of political institutions. These political institutions, on the other hand, give rise to the obligation; hence it appears to be circular in its justification. Does this amoral description of obligation appear useful to us? To argue that obligation for a particular law only relies on our feelings appears like a weak argument for actions such as civil disobedience, etc.
2) How does this feeling for political obligation work with our increasingly cosmopolitan world? In particular I'm thinking of second/third generation immigrants who have some connection with both their adopted country and historical home.