This depends on a number of things, primarily on the author's and translator's permissions. If they're not specified, you should credit them clearly and there might not be any issues, but it's a bit more complicated.
Law can be a little weird in regards to copyright, and it's an established law that a translation is your individual, creative work protected under its own copyright. Issues start to crop up once there is monetary gain, but as long as you're publishing it as a translation (a dependent work, iirc, there's a legal term for that), not as your own original fiction, I'm pretty sure there's no issue. This might differ in various countries though.
If you're editing an existing translation though, things change, because you would be claiming a part of someone's work as your own. I've honestly no idea how things would legally work in that scenario, but with my limited knowledge, I'd say you either need explicit permission from the translator or you need to rewrite all of it, or you're breaking the law.
Who is going to sue you?
