There's different types of regulation to consider.. There's spectrum licensing, radio user licensing, and product certification.
2.4 GHz is considered an ISM band meaning it's license free meaning you do not have to purchase a license from the government to use that physical chunk of spectrum. There are certain chunks of spectrum (frequencies) that are auctioned off by the government. This gets you exclusive usage to that band, across a country or in certain parts. The government will (is supposed to) enforce the spectrum so unlicensed users aren't clogging things up. You may not need a spectrum license for ISM band usage, but you still need to be using certified products.
Next you have user licensing like HAM radio operators. Amateurs are legally required to have licenses to operate the radios. I'm not sure whether a HAM radio license also includes a fee for spectrum.
Last (but I'm sure there's probably more regs), you have the certifications for the product itself. If you're in the US, this means doing FCC testing and getting an ID for your product. Each country typically has their own regulatory body. A certified product means your OK on duty cycle, TX power, etc. There's other tests as well especially if you're dealing with wearables but that's a different story.