Bugs caused by edge-cases in data are exactly the types of bugs that are usually not caught in smoke tests.

In my experience with large regulated systems, the engineers writing the software don't have the expertise to even know what the correct specifications should be in most cases, and especially in edge cases. Software engineers are not experts in customs and immigration legal requirements and would be relying on heavily on guidance from experts in those fields to determine the proper rules to apply.

In my experience with bugs like this, it is usually scenarios that all parties involved in the design did not consider... especially when implementation is rushed due to tight deadlines.