Your divorce decree does not require the permission of your ex to move.
Simply give him at least 30 days notice that you are moving - put it in writing and send it certified, return receipt requested! - then pack it up and move it out.
Just out of curiosity, what if the divorce decree does say you need the ex's permission? Im in a similar situation and I am preparing a letter to send to my ex asking permission because my fiancee and I are planning on moving to PA when my oldest daughter graduates from school - she is in a special school due to an autistic spectrum disorder. I'm afraid that he is going to say no just to be spiteful and I know I have to file a motion and goto court. But Im nervous, fearing the judge will not allow us to move. I know that no one can predict what a judge will decide. My ex only contributes what he is legally obligated to and does nothing more for them. The 2 older children do not want to see him but he still sees the 2 younger ones, one day a week for 6 hours. Should I request a best interest investigation if my ex denies the move?