Freedom of association
In its simplest form, freedom of association places no restrictions on which friendship circles, clubs or societies we choose to join, but as this is taken very much for granted, the term usually refers to membership of trade unions, different religions or political movements if it is used in the media. That being so, its connection to the right of peaceful assembly is made clear since workers’ strike action, faith-based disagreements and mass demonstrations all tend to make headlines.
Another facet of this freedom is that membership organisations have the right to lay down criteria for joining, such as annual fees and age limits. They also have the right to set other appropriate rules and carry out activities in pursuit of their particular interest ~ indeed, it would be odd if they did not ~ so meetings, presentations, outings and events are all part of the enjoyment of associating with like-minded people.
It is unlawful to force someone to join or leave a trade union, for example, as a condition of employment or for this to result in discrimination. It is entirely the choice of the individual employee, who may even join a different union to the one their colleagues belong to.
(Image [cropped]: John Morris at Flickr.com / CC BY-NC-SA 2.0)