Both the fifth amendment and the fourteenth mention "due process" as in: no person may be deprived of life, liberty, or property without due process of law. The

Both the fifth amendment and the fourteenth mention "due process" as in: no person may be deprived of life, liberty, or property without due process of law. The fifth fifth applies to the federal government, and the fourteenth to the state governments. When the government passes a law that infringes on a person's right, one way a person can challenge it is to claim that the law violates (substantive) due process. The idea is that government has to have a reason for depriving a person of his right. How important the government's reason has to be depends on the importance of the right being infringed. If the right is "fundamental" (1st amendment, voting, interstate travel, or privacy,) then the government must have a very good reason for infringing the right and it must not infringe more than necessary. This is "strict scrutiny". If the right involved is not very important, the government need only show that it had some acceptable reason (the law must be rationally related to a legitimate government purpose.) This is rational basis. Every law that fails rational basis must also fail strict scrutiny. But not every law that fails strict scrutiny must also fail rational basis. The vast majority of the laws pass rational basis. It's true that the law being challenged has to relate to the fifth or fourteenth amendments, but that's not a very hard test to meet. Almost anytime a person would legitimately want to challenge a law, it would be because the law is depriving him of some right. And in every such case, the law must at least have a rational basis. This is case here. The traveler has a right to travel, the government was going to deprive the traveler of this right. The government must have a rational basis at least.