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Part 15.235 of the rules covers operation in this band. There is no mention of the modulation method in this section so spread spectrum may be used but the out of band limits may be a limiting factor since spread spectrum can require a wide bandwidth depending on how fast frequency hopping is deployed.
As a practical matter, the field strength limit is to be measured as described in Part 15.35 which could be a problem for someone who builds their own transmitter and lacks the proper test equipment. Perhaps a commercial certified unit would be the easiest approach for operation in this band.