Can a RN (registered nurse) get a TN VISA with an Associate Degree?

My friend has an Associate Degree in Nursing and a RN license from USA to work as a nurse. Both AAS degree and BSN degree can work as NURSE.
Is there an immigration rule that one needs a BSN degree only to get a TN VISA?

View this post on my blog: http://travelnursesuccess.com/can-a-rn-registered-nurse-get-a-tn-visa-with-an-associate-degree