The mother of a brain-damaged girl says the law should be amended, after the High Court ruled her daughter could travel abroad to receive treatment.
Five-year-old Tafida Raqeeb has been on life support at the Royal London Hospital since suffering a traumatic brain injury in February.
Health bosses had tried to block attempts to take her to the Gaslini children's hospital in Genoa, Italy.
Tafida's mother Shalina Begum said: "The law now needs to be revisited".
The Charter of Fundamental Rights of the European Union, which rules a "child's best interests are paramount" in all healthcare decisions, was ratified in 2000.
Mrs Begum said the "country has evolved" since the law came into effect.
Speaking on the BBC Today programme, she called for a "clear law that says if there is a reputable hospital prepared to treat a child then there should be no blocking".
UK specialists had argued any further treatment of Tafida, who suffered a brain haemorrhage, would be futile.
Bosses at Barts Health NHS Trust, which runs the hospital in Whitechapel, have argued that ending Tafida's life-support is in her best interests.
Tafida's parents, both practising Muslims, argued Islamic law said only God could take the decision to end her life.
The High Court ruled on Thursday there was no justification to stop the child being taken abroad.
Mrs Begum said there had been a "complete meltdown" in the relationship with doctors at the hospital since the ruling.
"We don't talk, we don't speak. They just walk past," she said.
A Department of Health and Social Care spokesman said: "Decisions around withdrawing treatment are never easy, and it is important that families and medical experts reach agreement in the best interests of the child.
"Where this is not possible, as in this sad case, it is right the Courts are asked to make a decision."