I am not a native speaker, so I cannot entirely sense the difference in the meaning of the following two sentences:
An action can only be legitimate if sufficient justifying reasons can be addressed to all concerned (affected) parties...
and:
An action can be legitimate only if sufficient justifying reasons can be addressed to all concerned (affected) parties...
I do understand that, in the second clause, the only if is employed to signify a strong formal condition, i.e., that an action can be legitimate only if that condition is met.
However, I do not understand the first clause (...only be legitimate if...). What is the emphasis of this first clause? I would very much appreciate your help since I am translating an academic text into my mother tongue, and thus need to be very precise when it comes to nuances in meaning.