Can you specify what country you have in mind and the laws around union elections? I think that would help because the more I read about union laws in diverse

Can you specify what country you have in mind and the laws around union elections? I think that would help because the more I read about union laws in diverse place, the more I realize that it's not a even field. A set of questions that comes to mind in regards to union legal framework: is a union mandatory? if yes, starting what company size? If not, what can trigger a election? What is the status of the employee running in a union? Is there legal recourse in the event that some of those employee are terminated without cause?