 What “justification” is taken to refer to varies between authors. Douven (2006, 2009) and Lackey (2007, 2008) argue for a norm of rational belief. Note that  (JNA)  does not require that you believe what you say: all that it requires is that it is (or would be) rational for you to believe it. As such,  (JNA)  classifies selfless assertions (which are disbelieved, but rational to believe) as appropriate, a prediction that Lackey (2007) takes to be a crucial advantage of  (JNA).