From the post "Yes, the FCC might ban your operating system" - https://prplfoundation.org/yes-the-fcc-might-ban-your-operat...
2.1033 Application for grant of certification. Paragraph 4(i) which reads:
For devices including modular transmitters which are software defined radios and use software to control the radio or other parameters subject to the Commission’s rules, the description must include details of the equipment’s capabilities for software modification and upgradeability, including all frequency bands, power levels, modulation types, or other modes of operation for which the device is designed to operate, whether or not the device will be initially marketed with all modes enabled. The description must state which parties will be authorized to make software changes (e.g., the grantee, wireless service providers, other authorized parties) and the software controls that are provided to prevent unauthorized parties from enabling different modes of operation. Manufacturers must describe the methods used in the device to secure the software in their application for equipment authorization and must include a high level operational description or flow diagram of the software that controls the radio frequency operating parameters. The applicant must provide an attestation that only permissible modes of operation may be selected by a user.
2.1042 Certified modular transmitters. Paragraph (8)(e) which reads:
Manufacturers of any radio including certified modular transmitters which includes a software defined radio must take steps to ensure that only software that has been approved with a particular radio can be loaded into that radio. The software must not allow the installers or end-user to operate the transmitter with operating frequencies, output power, modulation types or other radio frequency parameters outside those that were approved. Manufacturers may use means including, but not limited to the use of a private network that allows only authenticated users to download software, electronic signatures in software or coding in hardware that is decoded by software to verify that new software can be legally loaded into a device to meet these requirements.