Churches and religious organisations are a law unto themselves. Under UK law it is unlikely that being baptised is regarded any differently to any other form of religious confirmation.
What is different is what the religious institution does with the commitment in the future. If a Catholic no longer wishes to attend church they simply walk away. The same is true for CofE and many of the other mainstream faiths. However for a witness child the baptism is not a mere statement of faith it is a set of rules they become bound to for the rest of their lives. If they chose to walk away from the faith they also lose family, friends and support.
In the UK there have been talks that encourage parents to persuade their children to be baptised at an early age as this will supposedly act as a protection for them. Watchtower articles have historically carried the same message. It is a cruel and heartless attempt to entrap children before they have really understood what they are letting themselves in for. The sad truth is that there is no legal protection for minors who chose to be baptised before the age of 16 and certainly no restriction in law.