The Chen case is interesting. A small child is an EU citizen (Irish!) and the parent(s) are not EU. The child has treaty rights as an EU/EEA citizen, but can only take advantage of them when the parent can come along.
In the UK, the home office interpretation of this case allows the parent(s) to accompany the minor child, but the parent is not allowed to work and must have sufficient resources. This narrows the set of people who can take advantage of the Chen case to wealthy families who can afford to live in the UK without working (Hint: don’t live in London!).
A good summary of the case and it’s implications is at http://www.immigrantcouncil.ie/chen.pdf