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The movement has also pushed many publishers to allow scientists to upload their research to Open Access repositories like Arxiv.org — which are currently the largest legal source of Open Access papers. The movement has been so successful that even the government has shown signs of supporting it. For instance, in 2013, the Obama administration mandated that copies of research conducted through federal agencies must be uploaded to free repositories within 12 months of publishing.
Cornell University Library's arXiv smile

Caveat: The Subject line of this post, "Freedom of access to academic research" does not appear to utilize the correct word, conflating freedom and free. The OP's article is about "free access" (without cost at point of service). By contrast, "freedom of access" would tend to indicate a right to access. (For example: Most citizens do not have freedom of access to classified government documents.) As pertains to this article, Sci-Hub and LibGen allegedly perpetuated mass violation of copyright laws, in order to make materials available for free.