The GPL depends on the body of copyright law for enforcement. An entity that violates the GPL by, for example, making a derivative work and not releasing the so

The GPL depends on the body of copyright law for enforcement. An entity that violates the GPL by, for example, making a derivative work and not releasing the source, legally would be held to account by the owner of that particular project's copyright. This works because copyright prohibits copying software except by express permission of the copyright holder. The GPL grants anybody the right to copy the software as long as they abide by the license. Once you violate the license, then your right to copy or distribute the software is revoked.