I’ve never heard of such a thing (which doesn’t mean it doesn’t exist). I can’t imagine something like that would carry more weight than a BA in English or journalism or another relevant discipline with internship or publication experience (such as working as a copy editor for a university newspaper). Maybe even a minor in English would be enough.

Edit: I have heard of specializations for English degrees, such as expository writing, creative writing, or technical/professional writing, which might show a potential employer that the student focused their studies on something other than literary criticism.

I copy edit for a living, and I do not know of such a certification.

I think it has to do with grammar and punctuation, perhaps…?

I could be mistaken, of course.

When I was interviewed for jobs like that, the interviews included proofreading tests. No certification was mentioned.

No doubt there are courses available that will award you a certificate of completion. I believe EEI (formerly known as Editorial Experts, Inc.) is one such source, and there are probably very many with varying degrees of credibility behind them. I could offer a one-day workshop and give you a certificate of completion at the end, but what would that mean? There is no such thing as a copyediting credential, more’s the pity.

@Jeruba Indeed!

Try here if you want a program of study. This may also be of interest. I searched on editorial practices and journalism and copy editors and journalism. The second search phrase got me here, The American Copy Editors Society.