Iowa Code § 326.21
In the absence of an agreement with another jurisdiction, the department may examine the laws and requirements of such jurisdiction and declare the extent and nature of exemptions, benefits, and privileges to be extended to vehicles or owners of vehicles properly registered or licensed in such other jurisdiction. The department shall consider the interests of the state of Iowa and its citizens, the interests of the other jurisdictions and their citizens, and the benefits which will accrue to the economy of the state of Iowa from the uninterrupted flow of commerce in declarations made pursuant to this section. Each declaration shall specify that the extent of exemptions, benefits, and privileges is subject to revision without notice upon adoption by the general assembly of legislation in conflict with the terms of any such declaration.
Iowa Code § 326.21
2012 Acts, ch 1093, § 28