my understanding is most (if not all) porn tube sites are 'unlawful' in that users can upload pirated content to the site (not supposed to but they CAN) ... in fact, if you think about it, basically all of the full scenes uploaded to tube sites are pirated content as most porn companies have their own website to host content (which members pay to have access to) or release it on dvd so they would not want people to be able to access it for free on the tube sites as they would be losing $. but what many of the more popular tube sites, such as xvideos, do is work in accordance with companies so that if they submit a request for video removal, it is done so promptly. kinda like what youtube has to do (in terms of taking down music videos that are posted by regular users and not the artist / record label on their vevo channel). xvideos has just about the fastest removal rate, a lot of old scenes are left up due to companies now being defunct or not caring too much about scenes shot 3, 4, 5 years ago but basically any FULL SCENES shot now (2012 to present) and uploaded to xvideos is almost guaranteed to be taken down within days, weeks and at worse a few months, depending on when the porn company catches whiff of it on the site. some up-loaders, knowing this, will intentionally put misleading titles on their videos and sometimes even tell you not to mention the girl(s) in the video's name in the comments and may even encourage you to down vote the videos so that they are harder for companies to find. and some tube sites such as xvideos and pornhub, not only work in accordance with companies but actually now HOST profiles for established porn companies where the companies post mini clips of scenes to the site.
so as far as i understand it, it would be hard for a tube site to be referred to as 'legal' unless they regulated EVERY thing posted or only allowed porn companies to upload content (i believe pornotube was doing this 5, 6 years ago, not sure if they still are now)
