The scenario described relates to A. Federalism, as it involves the interaction between different levels of government (federal and state) in addressing the minimum wage law. However, if you're looking for the aspect of the government structure where the legislative (Congress) and executive (President) branches interact to enforce laws, then it might also relate to B. Separation of powers or C. Checks and balances.
If the focus is on Congress making the law and the President enforcing it, B. Separation of powers is likely the most appropriate answer.