"Shall Issue" are states where if you apply for CCP you WILL get it as long as you pass requirement. In WA, its just a background check and be 21yrs old.
TX its background, gun course and 21 (unless your in the military but that's a stupid point because you need to be in for two years. Puts you at 20 so your only getting it a year early....I'm not sure but heard they did it for military police. So guys can leave base without checking in their sidearm)
Other states, like CA, its "May-Issue". They look at reason you want want it and decide if they like your reason. So two people, neither with criminal history, both with exact same reason, both have firearm training, want a permit...one may get it, one may not. There is no standard. It's totally up to who reviews your application.
So lets say Florida was a May-Issue state. They could look at Zimmermans app and say no. Look, you already shot someone or you've been on trial for murder, so what if you were found not guilty.
But since they are a Shall Issue state.....no criminal record? Your trained? Here ya go.