Brett, 51, and Naghmeh, 45, took their 5-year-old son Ashya King out of the hospital where he was being treated for a brain tumour and travelled to Spain.
"They cannot be charged with abducting their own child"
Officers issued a European Arrest Warrant on the grounds that the couple had neglected their son, which led to the Kings being separated from their son - who has been taken to a Spanish hospital under guard - and imprisoned.
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However senior lawyers have since said that there is little evidence the pair had committed any offence or that police undertook a satisfactory criminal inquiry.
Barrister John Cooper said police risk appearing as the ‘enforcement arm of medical opinion’.
He said: "The police are there to protect citizens and the easy transition to uncritical enforcers of other powerful interest groups is troubling.
"We should remind ourselves that this was a case of two adults who had parental control, who lawfully took their child from a hospital, and by all accounts cared for his welfare in an attempt to give him a chance at life."
Edward Grange, who specialises in extradition cases at London law firm Hodge Jones & Allen, added that he was deeply concerned at the Kings’ treatment.
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He said: "My concern is that they are seeking to use this warrant while their investigations are ongoing and that is most unusual. We have not been told if the couple involved have committed any crime.
"They cannot be charged with abducting their own child. There was no protection order in place regarding the boy so they have not absconded with the child against the orders of a court."
Deputy Prime Minister Nick Clegg has also backed calls for them to be reunited, insisting that it is "not appropriate" to "throw the full force of the law" at the parents.
He said: "A little boy is on his own in a hospital, doesn't speak Spanish, is cut off from his parents and his siblings and I would like to see him together with his family as soon as possible.
"As far as I can make out, this is a family in a state of real anguish who have taken this exceptional step of moving their sick child to another country because they think that's what is best for their child."
The family took Ashya from the hospital last Thursday and travelled to France with him and his six siblings before heading to the Costa del Sol in southern Spain.
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They want him to receive a treatment which they say was not made available to him on the NHS.
More than 115,000 people have signed an online petition demanding Ashya is reunited with his parents - will you be signing? Let us know via the Comments Box below now.