Why does declaration is valid, and intialization is not in switch statement

I've already read this " Why can't variables be declared in a switch statement? ".

However, I still can't understand why does this work:

switch(n){
case VAL:
    int a;
    ...
    break;
case OTHER_VAL:
    a = 12
    ...
    break;
}

suppose to this:

switch(n){
case VAL:
    int a = 12;
    ...
    break;
case OTHER_VAL:
    ...
    break;
}

I understand that that initialization part is bypassed, at the label val, so why does the declaration part isn't?.