Ragwort is covered under the 1981 Wildlife and Countryside Act. This is what the Act says
Section 13
"(1) Subject to the provisions of this part if any person
(a) intentionally picks, uproots or destroys any wild plant include in schedule 8 ;or
(b)Not being an authorised person intentionally, uproots any wild plant not included in that schedule.
he shall be guilty of an offence. "
This means that it is illegal to uproot ragwort unless you are the owner or occupier of the land where it is growing or have their authorisation, or if you have written authorisation to uproot ragwort from the local authority, Environment Agency, a water undertaker or a sewerage undertaker
S.13(1)(a) Protects completely a series of rare plants which are listed under Schedule 8 of the Wildlife And Countryside Act
and then
S.13(1)(b) creates an offence of uprooting any wild plant that is not listed under that Schedule unless you are an authorised person.
There are cases reported on the internet of people doing this with ragwort on nature reserves where, misled by inaccurate campaigning by agricultural groups, they think they are doing the right thing.
There are also cases where other similar looking plants have been removed.
Ragwort is also mentioned in The Weeds Act 1959 , where you may be ordered to control ragwort on land but are not required to do anything at all in the absence of one of those rare orders, and in the Ragwort Control Act 2003, which rather wierdly provides for the production of some advice to people, which the government could have done anyway.