The constitution is a "contract" signed among sovereign states that have all legal authority over their own borders with only a few exceptions that are defined within the enumerated powers of the constitution itself and the tenth amendment specifically says that all powers are reserved for the states with the exception of powers delegated to the federal government (such as declaring war) and things the constitution prohibits states from doing (such as states minting their own money). This creates a separation (or wall) of legal authority between the state and federal government because it prohibits states to undertake powers delegated to the federal government but also states that all undefined powers (or unwritten powers in the constitution) are reserved for the states. A power will either belong to the federal government or will belong to the state government but can never belong to both at the same time. The only legal authority the federal government has over our own lives is enforcing powers granted to it in the constitution while all other legal authority outside the limited defined powers of the federal constitution is reserved for the state governments. This gives each individual state government almost all legal authority over our lives while the federal government has very little authority since it only has a few limited powers granted to it in the constitution.