The Consumer Product Safety Commission requierments regarding electric bicycles are:
An electric bicycle which not brake those rules is considered as rgular bicycles and all that entails from it.
Each state has the possilibty to add more requiremnets and some of them did add some.
If there is no law in your state, then the above rules should be considered.
If you want to read the offical document, click here: Requirements for Low-Speed Electric Bicycles