Based on the excerpt, James Madison believed that federalism is needed in government because it limits governmental authority in order to avoid abuse of power. This is evident from his discussion of the division of power among different governments and departments, which creates checks and balances.
As for the role of the judicial branch of government, the statement that best represents it is The judicial branch has the ability to declare a law unconstitutional. This key function helps ensure that laws and actions of the government align with the Constitution.