Is watching pirated series and films a sin, and does the ruling for a thief apply to the viewer?

It is not permissible to download or watch movies and TV series that contain impermissible elements, such as the display of nudity, advocacy for evil, or the beautification of obscenities. As for what is free from such impermissible elements, it is permissible to follow it, provided it is not published without the permission of the copyright holders, as the violation of legally protected copyrights is a forbidden transgression.