An exception can only be made if the information is “pertinent” to the case, authorities decided on Wednesday, as reported by newspaper 20 Minutes on Friday.
The move was suggested by the political left as a way to prevent the racial prejudice that can arise from releasing the origins of those involved in criminal activity.
But right-wingers counter that releasing such information is a matter of transparency.
Opinions on the issue differ throughout the country.
Police in Neuchâtel and Fribourg only release nationality “if that adds value”, Fribourg police spokesman Gallus Risse told 20 Minutes.
“It's about using common sense and avoiding stigmatizing a specific nationality,” he said.
However police in the cantons of Geneva and Vaud take the opposite stance.
There, a suspect's nationality would only be kept secret if it could identify him.
“We wouldn't say that he's Chinese if he lives in a small village and he's the only Chinese person living there,” Pierre-Olivier Gaudard of Vaud police told the paper.
“It's also a question of transparency,” he added.
Zurich lawmakers adopted a further initiative on Wednesday to stop certain people being subjected to multiple police searches based on their appearance.
Officers must now give a receipt to anyone subjected to a stop-and-search.
The move was proposed by two politicians in July as a way to stop racial profiling.
“In this way, officers will not only need a valid reason to carry out a check, but it will prevent certain people being searched several times over a short period”, politician Ezgi Akyol told 20 Minutes at the time.
“That would complicate our work in the street and would even be counterproductive”, Martin Niederer, Vice President of the Zurich city police association, responded to the paper.
“If we find nothing during a first search, that doesn't mean that, during a later check, we wouldn't find something.”