Which part of the following is constitutional regarding state regulations?

In the context of federalism, state regulations must align with the commerce clause of the U.S. Constitution, which gives Congress the exclusive power to regulate interstate commerce. States have limited authority when it comes to legislating in areas that can interfere with or burden interstate trade.

The correct answer indicates that none of the choices presented are constitutional regarding state regulations. This is due to the potential conflicts that such state regulations could create with federal law. For instance, imposing restrictions on routes based on vehicle size could disrupt the flow of interstate commerce, which is a federal concern. Similarly, requirements for liability insurance could vary significantly from state to state, leading to inconsistencies that complicate interstate transport. Regulating bills of lading also falls under the purview of federal law, as these documents are standard in the shipping industry and are crucial for interstate logistics.

Therefore, each option highlights a potential infringement on interstate commerce, reinforcing why they may be deemed unconstitutional when considered in the context of federal authority and the principles set forth in the commerce clause.