There's a limited amount of adjectives that can only be placed before like: fiecare om, primul om, orice om, un anumit om, niciun om.
And there are some which are always placed after:
- those stating nationality, religion, social or geographical status etc.
- those that describe a shape or color (red - rosu, twisted - răsucit)
- those that describe a state (used - folosit, pregnant - gravidă)
However most can be placed either before or after, but placing it before puts emphasis on the adjective.
So in this particular scenario, the meaning of the English variant looks to empathize that you are a good citizen, so the Romanian translation has bun placed before instead of after. Poets often do this to help with rhymes.