If you have not transferred your copyright to an academic publisher by contract, you are the copyright holder for your works, and so you have the right to put it in open access. When publishing an article in a journal or book, authors often sign a copyright transfer agreement, and the general terms and conditions of the publisher apply. Authors wishing to keep at least some of their rights can use the SPARC Author Addendum. Of course, the publisher must give its consent to any addendum.
According to the Swiss law (art. 382 par. 3 of the Code of Obligations), the author can publish the article elsewhere 3 months after its publication, subject to a contractual agreement to the contrary.
Most toll-access publishers allow self-archiving (green OA road), sometimes after an embargo period.
You can check the policy of each journal on the SHERPA/RoMEO website. Open Access Button has created a very convenient tool, Shareyourpaper.org, allowing authors to check automatically and easily how they can share legally their work.
Open Access Button has also created another tool, called Direct2AAM, to give instructions for authors to obtain an Author Accepted Manuscript (postprint) from their Journal Submission System.
The Graduate Institute repository archives the research produced by the Institute. It contains records for all books, book chapters, journal articles and working papers written by Graduate Institute professors and researchers. A pdf file with the full text can be attached to the records of journal articles or papers, whose access can be open or restricted, depending on the statute of the file. If necessary, an embargo period can be set. The repository is registered in OpenDOAR, and allows Graduate Institute researchers to meet the OA requirements of their funders.