This question already has an answer here:
Ever since PPCG was created, answers using builtins have been an issue for challenge writers. Sometimes, an interesting challenge can be posted, only for some languages (not necessarily golfing languages) to have a builtin function that does all the work. Some people don't mind these answers, others seek to ban them. My views can be summed up by this comment.
Now, banning builtins outright isn't what we should do. Lynn puts it much more elegantly in that post, but quite often, answers without builtins get more upvotes then answers with builtins. Upvotes shouldn't matter to the more active users, but they do have a negative effect on voting: more votes equals more visibility.
However, builtin solutions aren't good answers. A good answer contributes something new, something interesting to the site. And 10 answers consisting of the same function do not do this. One suggestion is to combine equally trivial answers, but that hasn't always worked out, or been implemented. Basically we have to face it: builtin answers will be posted.
Yet, there may be a solution that satisfies both sides of the argument: forcing non-builtin answers to be posted with builtin answers. I'd be much more inclined to upvote a Mathematica answer that actually implemented goat recognition, rather than relying on a builtin function.
Therefore, I am suggesting allowing a rule in challenges where, if the challenge is fairly trivial, the challenge poster can force answers to post both the builtin and the non-trivial code in their answer. This meta post is here to ensure that the challenger can enforce this rule, if implemented.
What do you think?