Final answer:
The layer of employment law that is most restrictive to an employer in Iowa can vary. While the ADA sets federal standards, state and local laws can be more restrictive, and without specific context, it's not possible to determine which layer is most restrictive. Employers must comply with all applicable laws, and the most restrictive regulation generally takes precedence.
Step-by-step explanation:
In the context of employment law, the layer that is usually most restrictive to the employer in Iowa can vary depending on the specific employment issue. Generally, federal laws, such as those enforced under the Americans with Disabilities Act (ADA), set minimum standards for employers to follow. However, state or local governments have the authority to pass laws that are more restrictive than the federal baseline. In the case of Iowa, without specific context, it is not possible to definitively say which layer is the most restrictive without examining the particular employment practice in question. It is important to note that employers must comply with all levels of laws, and in cases where there are multiple regulations, the most restrictive one typically applies.