There is no custody, but my son lives with me and visits his Dad. He has a passport and I have taken him before, with permission of father. This time we want to stay for six months. Should I carry a letter with his father's permission, and what if he does not agree to this?
This is really an international law question, not an immigration question. You could run afoul of the Hague Convention on International Child Abduction. You should consult with a family law attorney who is experienced in international child custody issues BEFORE you take your child about the country. I've added those practice areas to your question.
Estate Planning Attorney
This is really a question for an lawyer that deals with immigration issues. I have added immigration to your category. Also I would call the Embassy for the UK and ask them if there is someone there that can answer your question. It would also be a good idea to get a formal custody order in place.
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This is not an immigration law question, really. Not US immigration law question, anyway.
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