In the board game The Resistance are two factions, Resistance fighters and Spies.
Me and my friends had some debate if the Resistance fighters can actually use the Fail mission Card. 

My stand is yes, the resistance fighters can also use the fail card, because I didn't see in the rule book that they can't use the fail card.

The question here is, can the good guys use the fail card whether he has a reason to use it or not?

**Edit**  

based on the rulebook it is stated that 

> 
> The Resistance Operatives **must** select the Mission Success card; Spies may select either the Mission Success or Mission Fail card.
> 
> 
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the question is, does the must is just only a Highly recommended move? or a compulsory move? based on the dictionaries i have checked **Must** is used in different ways. 

**Edit** 

So most of the suggestions in the answers pertains to "The resistance cant use the fail card because they have no objective to do it so." 

That might be true to the plain The Resistance, but please mind that there are other modules/expansion packs in the Resistance that can give the Resistance an objective to fail a mission, 

one example would be **The reverser module** wherein in this module the reverser (resistance or spy) can reverse the output of the mission, if resistance member already know who is the resistance reverser they can talk to each other like, "Hey reverser, pick the reverse card and ill pick a fail card so that we are sure that in this round we will win even though we get other spy in the mission group". 

That is the main reason why i'm asking if the resistance can use the fail card. obviously in this expansion the good guy has already a reason to fail a mission., they can also fail the mission if he thinks that there is a reverser spy in the group and reversed the outcome of the game thinking that all of the resistance would vote success.