The Foreign Affairs Manual (FAM) is an instruction manual for Department of State Consular Officers. Inside, a set of reciprocity tables provides a baseline as to what the validity period and number of allowed entries will be for visas issued for nationals of a particular country. Consular officers do have discretion to alter the visa validity period, for example, but a new provision at 9 FAM 403.9-4(C)(b) is telling them to be judicious in not following the reciprocity tables and limiting visa validity.
The line of thought is that limiting visa validity may lead to complaints by the host government that consular officers are biased and the United States has failed to accord reciprocal treatment to the host government’s nationals. Such a practice may also result in an unnecessary increase in workload. The reapplication rate of aliens with limited visas is relatively high at many posts. Therefore, the period of time and the number of applications for admission for which a nonimmigrant visa is valid must not be restricted without due cause to less than that permitted by the reciprocity schedules and only with the concurrence of a consular manager. If due cause to limit the nonimmigrant visa is not present, then an officer should issue a full-validity visa. Limiting visa validity may also impact the equities of other parts of the United States government.
It makes good sense when you think about it. These tables are based on reciprocal treatment between countries. If consular officers are regularly ignoring the reciprocity tables and limiting visa validity, other countries can cry foul, and this presents a diplomatic problem.
~From a blog post by contributor, Adam Cohen.