Union members often stop paying their dues and just 'fall out of site.' There are many reasons for this, but a change of employment is the most common.
If the member continues to pay dues, even if he's not working, he can -usually- maintain his benefits. Otherwise, he gets a rude surprise at pension time.
Likewise, a union will often impose fines and other sanctions if the member has been 'working in the trade' outside a contract; nearly every form of employment apart from flipping burgrs is considered as 'working in the trade.'
It can quickly becom rather complicated; remember the role of seniority in the typical union structure.
When someone leaves a Union job, for any reason, it is usually best that they go to Union Hall and get a 'withdraw card.' This can help clarify matters later, should one ever again have to deal with that particular union.
Remember: the Union has absolutely NO hold on you personally, but they do control certain benefits and credentials. There is absolutely nothing to stop you from opening up your own shop, or working for a non-union shop ... but you can also be sure that the Union will not welcome you back should the times change - just like many other employers.
