實施「一地兩檢」的法律問題是，可否在不違反《香港基本法》的前提下設計出一套法律制度來達到在西九龍高鐵口岸實施「一地兩檢」的目的。文章分析了《香港基本法》下支持和反對「一地兩檢」的所有法律理據，以及把中外現行的三種「一地兩檢」制度安排移植到西九龍的可行性。在此基礎上，本文探討部分借鑑現有三種「一地兩檢」制度安排的可行性，並建議採用「一地兩檢」和「兩地兩檢」的混合模式。由於「一地兩檢」已是箭在弦上，文章接著分析香港政府方案的法理依據，並質疑全國人大常委會批准「一地兩檢」的做法，以及提出更符合中國憲法理論的落實「一地兩檢」的制度建議。

The legal issue facing the implementation of colocation of immigration, customs control, and quarantine at Western Kowloon High Speed Train Station is whether a legal mechanism can be designed to be consistent with the Basic Law. This paper analyzes all the legal grounds within the Basic Law either for or against the implementation of colocation at Western Kowloon. It then examines the feasibility of transplanting one of three existing colocation arrangements to Hong Kong, and explores the feasibility of partial borrowing of three existing models. It suggests to adopt a mixed model so as to not only achieve the objective of colocation but also relieve some Hong Kong residents’ concerns over colocation. Since colocation is already unavoidable, the paper proceeds to examine the legal justifications behind the HKSAR Government’s proposal for colocation, questions the appropriateness for the Standing Committee of the National People’s Congress to approve the colocation arrangement agreement, and suggests a modification to that proposal in order to make it sound and unchallengeable under Chinese constitutional theory.