Swiss voters go to the polls on Sunday to decide whether foreigners who commit serious crimes in their country should be automatically deported.
The proposal put forward by the nationalist Swiss People's Party, or SVP, has drawn fire from legal experts who say it could breach offenders' human rights.
Anti-racism groups have also complained because posters used to promote the deportation campaign show black sheep being kicked off the Swiss flag by white sheep.
Opinion polls published earlier this month indicate a slim majority of voters favour the SVP's plan over a government-backed alternative proposal that allows for case-by-case review.
Separately, voters will be asked to approve a plan to introduce a minimum tax for individuals across all of Switzerland's 26 cantons.