Since the 1940 National Electrical Code (NEC), there has been a requirement that recessed incandescent fixtures be connected by wire having insulation suitable for the temperature.
Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to email@example.com. Answers are based on the 2014 NEC. GFCI protection of dishwashers in dwelling units