Read the bold part, it explains it well how it can be enforced on the state level.
gc505 Posted:
The federal law (subject to the Tenth Amendment and Fifth Amendment and other Constitutional Law) trumps – or "preempts" – the state law.
Federal preemption
Types of preemption:
Two situations where preemption claims might arise: express preemption and implied preemption.
1. Express preemption occurs where Congress says within the statute 'we hereby preempt.' Here, federal laws are explicitly precluding state and local regulations.
2. Implied preemption has, within itself, three sub-categories: conflicts preemption, preemption because state law impedes the achievement of a federal objective, and preemption because federal law occupies the field.
* Conflicts preemption is where it is impossible to comply with both the federal statute and the state or local law. In this situation, the federal statute must be followed. It is, however, appropriate to have two laws, one federal and one state, that differ. The federal law, in this case, may be a minimum standard, while the state enacts a law to be more strict.
State law, therefore, would not be preempted. Preemption would only occur if the federal and state laws were mutually exclusive.