Laptops for example have an FCC label (take a look at the bottom of yours) as they have radio equipment on them in the form of a Bluetooth adapter/Wi-Fi adapter/3g modem.
It is that wifi adaptor maker that is responsible for ensuring that the radio stays in compliance.
The laptop maker generally will only need to deal with the rules from part 15B, unintentional radiators. The laptop maker won't have to lock down the laptop OS.