One of the most common misconceptions about ragwort is that it is in some way illegal to grow it. It is most certainly not. The law relating to this is mainly the Weeds Act 1959 but also the misleadingly named Ragwort Control Act 2003.
The Weeds Act means that in rare cases you may be ordered to control ragwort but in the absence of any such order you have not duties or obligations what so ever.
Before the recent outburst of irrationality over ragwort the Weeds Act was never used at all.
The Ragwort Control Act? Well this does nothing much really only let the government produce a code of practice which could be used in court in the really rare cases ( probably non existent) where someone is prosecuted for not complying with a rare Weeds Act order.
See Ragwort the law explained.