Medical cannabis products were legalized under certain circumstances in Britain on Thursday.

This photo shows a budding marijuana plant. [Photo: AP]

More than 80,000 specialist doctors are qualified to prescribe cannabis-based products. According to a guidance published by National Health Service, they are allowed to prescribe medical cannabis only when "there is clear published evidence of benefit" and other treatment options have been exhausted.

The new rule about medical cannabis came after the cases of two kids, Alfie Dingley and Billy Caldwell who had severe epilepsy which has been improved by cannabis oil treatments. Their parents' campaigns pushed forward with changing the legislation.

However, reactions to the law change from the public are not all positive.

"It's absolutely gutting and not what my campaign was about," said Hannah Deacon, Alfie Dingley's mother. She added that the guidelines meant people would struggle to access the oil her son had been given because scientific studies had not been carried out on the treatment.

Dr. Waqar Rashid, a consultant neurologist at St George's Hospital, called for medical trials for medical cannabis products.

"Even with the best will in the world we're looking at very selective numbers of neurologists prescribing this and it would need the infrastructure to support it," he said.

Britain is not the only country where medical cannabis is legalized. The United States, Chile, parts of Australia and parts of India also allow some use of medical marijuana. 

In October, Canada became the second country after Uruguay where weed is fully legalized.