PAs are required to have an established practice agreement with their collaborating physician.  Therefore, their scope of practice is clear, and they should be aware of their own limitations (just as physicians are).  If a patient fails to improve as expected, it should be the responsibility of the PA to assess the situation and change treatment, speak with the collaborating physician, and/or refer.  Just because a patient returns for follow-up does not mean that something was done wrong initially, nor does it mean that the situation is complex.  To mandate via law that a patient be seen just because they returned does not make much sense.