Pc Ben Hannam, 22, had also pleaded guilty to possession of a prohibited photograph of a child.
The 17-year-old listed 'areas to attack' including schools, pubs and council buildings.
Being a member of the organisation can lead to 10 years in prison.
National Action became the first far-right group banned in Britain since WW2
'I’m wondering if it was actually real life what I just watched.'
The US president said 'many sides' were to blame for the violence.
16-year-old 'tried to explain why nationalism makes no sense'