Declaring Local and Global in a function

I know it really looks like this but the problem is that the user can hack around this and call the function from anywhere in the code.
It's because functions are also glabal (stored at a constant position), so you could make a global variable store the function's address and then call the function from everywhere:

Global F3 ( )
F1
F3

Function F1 ( )
  F3 = F2

  Function F2 ( )
    'Do anything
  EndFunction
EndFunction

The problem is that the only thing which is actually only accessable from F1 is the symbol F2, the function itself in contrast is accessable from everywhere.
I know it would be nice to have it, I'd use it, too, but it's not possible, locals are only accessable from the function they belong to, except you do something like passing the variable's address to sub functions -> by reference parameters.Yes this would be a solution...