The national capital region refers to the region 'the capital and its surrounding area,' but in the succeeding law, it is clearly defined that 'national capital' part is 'Tokyo Metropolis' established in predecessor law (abolished law) and it imposes the obligation of Diet vote in order to change that part, and concerning 'the surrounding area' the new law took over predecessor law, in the way to delegate the lower rank act (government ordinance) and not to require Diet vote and flexibly change 'the surrounding area' part.
首都圏とは「首都＋圏（その周辺地域）」のことであるが、後継法では「首都」部分は前身法で既に首都と定めた「東京都」と明確に定めることで、その変更には国会の議決を義務付け、「その周辺地域」部分は下位法令（政令）に委任することで、国会の議決なく柔軟に変更できる余地を残す形で、前身法の首都の定義を継承している。