The legislative branch is made up of the House and Senate, known collectively as the Congress. Among other powers, the legislative branch makes all laws, declares war, regulates interstate and foreign commerce and controls taxing and spending policies.
The legislative branch drafts proposed laws, confirms or rejects presidential nominations for heads of federal agencies, federal judges, and the Supreme Court, and has the authority to declare war
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.
