I keep my blood ketone levels between 1.0-3.0mmol/L. I do this for pain control and mental clarity. It's called Therapeutic Keto. I use external products to keep my levels this high as my nutritional health would suffer if I ate 90% fat.

It takes time to find the exogenous ketone product for the individual body. Some I tried made me quite sick. The one I'm presently using is C8 powdered MCT oil and my body accommodates it well. I have to assume that these athletes were administered a product somebody wanted to sell the UK.

If hormones and fuel the body naturally produces were made illegal, just think about it. Higher testosterone levels give some athletes more power and stamina. As you said, the body produces ketones naturally. It's our survival mechanism. They can never make ketones illegal. Even if they ban exogenous ketone products, the athletes can still produce get high levels of ketones by diet.