The partial copy is a kind of copy produced by cropping parts of original materials. Illegal users often use this technique for plagiarizing copyrighted materials. In addition, original parts are not necessarily copied intact but may be modified by various techniques, and embedded into other materials, which make the detection quite difficult. In this paper, we propose a method of copyright protection applicable to partial copies aiming at the protection of line drawings such as comics. In order to cope with handwritten partial copies, we apply local feature matching with a database of copyrighted line drawings. Experimental results show that the proposed method not only performs good for detecting printed copies of line drawings, but also has effectiveness on the detection of handwritten ones, even if partial copies are embedded in complex backgrounds.