Substantive Due Process is a constitutional doctrine that protects certain fundamental rights from government interference, ensuring that laws and regulations are fair and just. This concept is rooted in the Due Process Clauses of the Fifth and Fourteenth Amendments, which require that the government not only follow legal procedures but also respect certain rights related to personal liberty and privacy. It focuses on the content of laws, emphasizing that some rights are so fundamental they cannot be infringed upon without a compelling justification.