REAL ID law sets forth requirements for US State Driver License and ID cards to be accepted by the United States federal government for "official purposes", as defined by the Secretary of the United States Department of Homeland Security. The Secretary of Homeland Security has defined "official purposes" as boarding commercially operated airline flights, and entering federal buildings and nuclear power plants, although the Real ID Act gives the United States Department of Homeland Security Secretary the unlimited authority to require a "federal identification" for any other purposes.
Which is a clear example of the United States Congressional Delegation of Power