Almost all governments have very specific rules and regulations related to the control of electromagnetic interference (EMI). Most spell out the parameters of what is allowed and methods of testing.
In the U.S., EMI guidelines for commercial equipment are handled by the Federal Communications Commission (FCC). The Code of Federal Regulations (CFR) section 47 Parts 15, 18, and 68 contain relevant information that all engineers should be aware of when designing class A and B devices.
The military has its own standards, which are significantly more stringent. These guidelines are detailed in a wide range of military standards, such as MIL-STD-461E, MIL-STD-464.
The International Electrotechnical Commission (IEC), via its International Special Committee on Radio Interference (CISPR), also created globally accepted EMI and electromagnetic compliance (EMC) rules.