Types of Preemption Analysis

1) Express Preemption
Congress expressly states that a federal law (a valid law that is not beyond the constitutional power of Congress) intends to preempt certain types of state legislation.  Even if the statute contains express preemptive language, there may still be an issue as to the scope of the preemption that Congress intends.  In addition to expressly stating an intent to preempt, Congress can also expressly state that it does not intend to preempt certain types of state legislation.

2) Implied Preemption  
Types of implied preemption:

1) conflict preemption
(a) a state law is in conflict with a federal law because it is impossible to comply with both at the same time (physical impossibility); or
(b) a state law is in conflict with a federal law because it interferes with the objectives of the federal law or is an obstacle to the accomplishment of the federal purpose.  To determine whether this type of implied preemption exists, it is necessary to determine the purpose of the federal law and how that purpose is impacted by the operation of the state law.  

2) field preemption: the federal government has fully occupied the field it has chosen to regulate.
To demonstrate that field preemption exists, the challenger must show that Congress intended to fully occupy a field and leave no room for even supplemental state regulation. When the Court is uncertain as to whether Congress intended to preempt the field, it will look at the nature of the regulated area. If the area regulated by Congress is an area in which the federal interest is dominant, the Court will be more inclined to presume that Congress intended to occupy the field (as in the areas of immigration or foreign affairs). If the area regulated by Congress is an area that has traditionally been regulated by the states (as in the area of regulating electrical utilities), the Court will be less likely to presume that Congress intended to occupy the field and may require that Congress make its intent to preempt clear and manifest.  Even if field preemption exists, there may still be a dispute as to the scope of the field that Congress intends to preempt.