It's important to respect the rights of creators over how their creations are reproduced or reused. Unless otherwise noted all sketches here are copyrighted by the artist who posted them and can't be reused without getting their permission first.
Similarly when creating and posting new art to SketchClub, artists are expected to share only their original creations or content which they have permission to use.
About.com has a handy Guide to Copyrights for Artists.
If you are a copyright owner or authorized representative of one please report alleged copyright infringements taking place on SketchClub by completing the following DMCA Notice of Alleged Infringement. Upon receipt the infringing content will be removed as appropriate from the community. Repeat offenders will have their accounts removed.
For additonal information required for a valid notification see 17 U.S.C. ยง 512(g)(3). Notices can be sent to dev@sketchclub.com.