My ex-wife and I have had joint physical custody (2 weeks on/ weeks off) for 6 years. She is wanting to get married and move to MS.

A court cannot prohibit a parent from moving out of state with the children.  However, since you share physical custody, I would imagine that she would need to file for a modification of custody in an attempt to gain primary physical custody.  A parent moving out of state qualifies as a material change of conditions that would serve as a basis for the modification action.  I recommend contacting an attorney who can further assist you. Diona M. Potter Potter Sieg, LLC   DISCLAIMER This answer is not intended to, nor does it create, an attorney-client relationship. It is not intended to constitute legal advice.  It is provided solely for informational purposes.  Do not assume that the legal theories I mention that pertain to GA will apply in your State. The facts of each case are different, and it is therefore critical for you to consult with a qualified attorney with whom you can share information which can be thoroughly assessed, so that you can get competent legal advice from which you can make an informed decision.