Possession of the class C drug for unlawful use can lead to a prison sentence of up to two years
Archived version: https://archive.is/newest/https://www.independent.co.uk/news/uk/crime/laughing-gas-breathalyser-nitrous-oxide-police-b2975925.html
Disclaimer: The article linked is from a single source with a single perspective. Make sure to cross-check information against multiple sources to get a comprehensive view on the situation.
For exactly these reasons, massively doubting the 'looming threat ', unless you count the threat of grifters milking money from the nanny state.
The threat i guess is more that it absolutely rots your brain. But that has nothing to do with whatever they are trying to accomplish