Final answer:
The statement that the Constitution ensures states retain all power not given to the national government is false, as the Tenth Amendment clarifies which powers are reserved for states, known as 'reserved powers.' The necessary and proper clause has expanded, not limited the powers of the national government.
Step-by-step explanation:
It is false that the Constitution ensures that the states retain all power not given to the national government. The Constitution does indeed create a federal system in which certain powers are allocated to the states and others to the federal government. Specifically, the Tenth Amendment confirms that the powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people. This amendment, therefore, establishes a class of powers known as reserved powers that are exclusive to state governments.
The necessary and proper clause, also known as the elastic clause, gives Congress the means to enact laws deemed necessary and proper for carrying out its constitutional duties. This clause has actually not limited, but rather expanded the power of the national government, as it allows Congress to pass laws beyond those expressly enumerated in the Constitution, provided they are in service of its recognized powers.