This question already has an answer here:
Consider a simple code where the coder imports an external library/module to solve a particular problem. In most cases it will be a built-in library, no problem. But what if someone creates his/her own library to solve the problem. Like
import x x.f()
In this way the problem will be solved in 13 characters. Which is unfair. Now you may ask the coder to add the library
x to the code too. But what if coder says he/she has created that language, and in that language, all you need to do is
f() to solve that problem. Now since golfing allows all the languages, the coder has the right to use his/her own language, which has a built in function
f(). How would you tackle this?