In Italy, up until the '80, conductors were allowed to ask a member of the orchestra to play a passage alone during rehersal. This led to some players being fired right away and their careers being ruined.
This until the labor unions banned it: as of today, only first parts (whose salaries are higher than those who play behind them) can be asked to play solo.
In my orchestra, the conductor insists that such a practise is still allowed "over the Alps" (in the rest of Europe).
I'd like to know how is this regulated in other parts of the world. Possibly, not just major Europe countries (like Germany, UK or France) but also in the US.
I assume this question is posed in regards of strings instruments only as the others are playing solo (or in small groups) by definition.