Archiving public data is a mandatory step before submitting a manuscript to the majority of the journals. However, information on whether and how researchers can access the underlying data is not a requirement at the moment.
In order to promote future researchers sharing and reusing data, a new policy will be implemented across the diverse range of Nature journals by early 2017. This new policy, which has been already tested on Nature journals since March 2016, will obligate authors to include statements reporting the data sets availability and restrictions when accessing these data.

According to the journal, this new policy aims at “offering consistent information on data availability in our papers will promote data reuse by future researchers”.

An example of the statement text for data archived at the EGA would be:

The data that support the findings of this study are available on request from the relevant Data Access Committee [e.g. https://ega-archive.org/dacs/EGAC00001000514]. The data are not publicly available due to [state restrictions e.g. “them containing information under controlled access”].

This announcement was published on September the 7th and can be read here: Where are the data?