it's not really a matter of "allowed" unless you're talking about broadcast television.

GoT doesn't have to follow the same rules, it's on a paid channel.

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Cersei's Game Of Thrones Nude Scene Cost How Much To Shoot?

https://www.cinemablend.com/television/Cersei-Game-Thrones-Nude-Scene-Cost-How-Much-Shoot-67684.html

Finally, cell phones were confiscated while shooting was underway, with TMZ reporting that only 4 people were actually on hand when Headey made Cersei’s famous walk of shame.
All of the extra privacy, security guards, permits and payoffs added up to a lot of money. The scene was shot over four days in Dubrovnik, Croatia at a cost of $50,000 per day. That adds up to $200,000 just to shoot nudity outside. Despite the expensive price tag for a scene without VFX, Game of Thrones is lucky that the scene moved forward and was shot, at all.