Not a good idea.
But if there is no court order you can apply for a Child Arrangement Order called a Prohibited Steps Order to prevent this under threat of arrest.
Fortunately, there is a lot of information on the Internet about Child Arrangement orders and the government have actually produced a guide on the subject which is here.
The different types of Child Arrangement order are:
1 A Contact Order which specifies when parent sees a child, it is no longer called "access".
2 A Residence Order to determine who the child lives with, it is no longer called "custody"
3 A Prohibited Steps Order to prevent a parent doing something with the child such as moving away either in this country miles away or taking the child to another country. Particularly relevant if there is a chance that the parent would go to another country and never return. The parent wishing to prevent the move would have to convince the court why it’s not in the best interest of the child to move. Friends, support, school et cetera et cetera all taken into account.
A Prohibited Steps Order is to prevent child Abduction and it’s one of the few areas of law for which legal aid is sometimes still available. It’s often therefore worth seeing a solicitor.
4 A Specific Issue Order to allow a parent to do something specific with the child such as moving away to another part of the country or indeed to another country. . The parent wishing to move would have to prove why it’s not in the best interest of the child to move.. Friends, support, school et cetera et cetera all taken into account. It would also encompass things such as changing school if the parents cannot agree, changing the child's name, and anything other specific.
The courts will not get involved in a Contact or Residence order unless the couple have been to mediation first. So the couple would have to try mediation even if it subsequently fails and the matter proceeds to court. That doesn't apply however if something is required in an emergency such as a Prohibited Steps Order.
Thank you for letting me assist you with your legal question. I am glad that I was able to help.
I am not certain whether that answers the question for you or not, but I am happy to answer any specific points arising from this.
It will be my pleasure to help you again either further with this or any future questions you have