Simply legislate that anyone in any safety critical job whether it's flying a plane, controlling a chemical plant, driving a hazardous goods truck or runnig a nuclear power plant, cannot have more than one job (relatively simple to track via social security/National Insurance number & tax records).
Might work in the UK, however certainly not in the USA...we have a constitution which prohibits such actions by the government, and if legislation was tried anyway, the first Federal court that it came before, would promptly strike such ill-considered legislation down.
PS: The US constitution was adoped just after the Brits were kicked out....long ago.