Instagram CEO Kevin Systrom with Instagram's Head of Fashion Partnerships Eva Chen (left) and Dazed Media's co-founder Jefferson Hack (right) at the event on Wednesday. Max Slater-Robins / BI Instagram CEO Kevin Systrom has explained one of the key reasons that the company censors pictures of female nipples: Apple's App Store has strict guidelines on what kind of content is allowed, and violating these rules could cause the app to be removed.

The #FreeTheNipple movement points out the double standard of censoring female nipples while allowing the male counterpart in photos. Celebrities such as Rihanna, Miley Cyrus and Chelsea Handler have all posted bra-less photos, only for Instagram to take them down.

Systrom said at the event hosted by Dazed Media on Wednesday in Shoreditch, London, that Apple's App Store has strict guidelines on the types of content allowed within apps, explicitly banning nudity unless the app is rated 17+. He went on to say that Instagram wants to appeal to as many users as possible, and gaining a higher age rating would prohibit younger users who want to view PG-13 content.

Despite the censorship, Instagram remains "committed to artistic freedom," according to Systrom. He went on to say that "in order to scale effectively there are [some] tough calls." For Instagram, banning some photos of female nipples is one of these tough calls.

Instagram is in a tough position when it comes to #FreeTheNipple. As Systrom pointed out, the internet hardly lacks pictures of female nipples, and viewing them on Instagram is not essential to the service.

However, there is an element of arbitrary censorship that comes with not banning male nipples too. The majority of users are unaffected, but it does work to erode the freedom of expression that the service wants to provide.

It's important to note that Instagram doesn't censor all female nipples on the app. The app's community guidelines explain that things like post-masectomy scarring and photos of women breastfeeding are allowed.

Systrom also answered questions on the rise of Snapchat, especially around coverage of live events. He compared it to Twitter or Facebook — neither of which directly compete with Instagram — and appeared unconcerned, even as celebrities sign-up in droves for a Snapchat account, potentially taking away content from Instagram.

Business Insider contacted Apple for comment on this article and we will update when it responds.