The Constitution discusses the powers of <u>legislature </u>in Article I--the longest Article of the Constitution--because the framers thought this was to be the most important and powerful part of government.
The framers of the constitution believed that the legislative arm of government will be most powerful because they wielded the power to make laws, which the executive and judiciary did not have.
The author means that even though Japan has a larger trading system (I assume that is what it's referring to) it does not exactly fit the same terms as a usual trading system would.
