Final answer:
The option that may not be regulated solely by state law is 'What minimum wage an employee must receive,' as it is also subject to federal regulation. States can set higher minimum wages than the federal standard, but not lower.
Step-by-step explanation:
The question asks which of the following may not be regulated by state law:
- How often employees must be paid
- What employers must do with unclaimed paychecks
- How soon employees must be paid after their employment is terminated
- What minimum wage an employee must receive
Among these options, setting minimum hourly wages is a topic that is regulated at both the federal and state levels, but the federal law sets the basic standard across the country. States can set higher minimum wages, but they cannot go below the federal minimum. As such, 'What minimum wage an employee must receive' is the option that may not be regulated solely by state law, as it's ultimately subject to federal regulation.
Other aspects like the payment frequency, unclaimed paychecks, and rules upon the termination of employment, are typically managed by state labor laws without preemption by federal law. Therefore, these aspects of employment can be regulated by individual state laws.