A new intelligence law, plus pension reforms and environmental policy, are the three issues being considered in today's referendum.
Proponents say the law, passed a year ago but not enacted, is needed to help Switzerland catch up with other countries who have stronger legal arsenals to counter cyber-crime, snooping or extremist attacks.
Opponents fear it will deplete civil liberties, do little to impede terrorism and chip away at Switzerland's long-vaunted neutrality.
Under the law, the Federal Intelligence Service and other authorities would be allowed to tap phones, cut through mail, infiltrate email boxes, keep tabs on internet activity, and deploy hidden cameras and microphones to monitor suspects who are deemed a clear threat, but only if authorised by the federal administrative tribunal and federal counselors who have oversight.
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Guy Parmelin, a member of Switzerland's seven-person executive council and the head of the defense and public security department, says authorities believe current Swiss laws are not "sufficient in the face of constantly evolving threats."
But an activist group whose name translates as "Snooping State" has countered that private life will be jeopardised. All emails, Facebook posts and text messages will be sought and intercepted, as part of "mass surveillance," the group says.