father to turn custody over to mother

[vlmitcham]

My ex husband had sole custody of my 17 year old son until he kicked him out of the house on 08/13/09. He is relinquishing custody of him to me. Is a letter confirming this that is signed by my ex, me and 2 non-family witnesses legal to show me being the custodial parent until we can both get to the court and file the change?