If federal law aims to occupy a field for a purpose different from state law, what happens?

When federal law aims to occupy a field for a purpose that is different from state law, it generally means that there is an intention for federal law to govern that particular area of regulation, although the purposes of the laws may not align. In this case, the statement reflects that the federal law does not preempt state law.

In legal terms, preemption occurs when federal law overrides or displaces state law based on the Supremacy Clause of the U.S. Constitution. However, preemption can be explicit or implicit. If the federal law does not indicate a clear intent to occupy the field or to preempt state law entirely, and if there's no direct conflict between the laws, then both can coexist and the state law remains applicable.

Thus, in situations where federal law occupies a field but does not clearly preempt state law, state law can still operate alongside federal law, which is reflected in the provided answer. This understanding highlights the complexities of federalism, where both levels of government have their respective roles and regulations, unless federal law specifically indicates it is intended to be the sole authority in that area.