The Senate has decided that the police should not be allowed to use electroshock stun guns during forced deportations.
Last October, the House of Representatives had voted in favour of Tasers, despite United Nations concerns over the guns.
Justice Minister Christoph Blocher said the main risk was that these weapons would be used too easily. Tasers are already authorised by several cantons for police work.
The UN Committee against Torture recently judged the guns to be a potentially lethal form of torture and urged Portugal to reconsider a decision to arm its police with them.
While Tasers are not technically considered lethal, some authorities and non-governmental organisations also question both its degree of safety and the ethical implications of it use.
The House of Representatives will now have to reconsider its earlier position.