An announcement in the federal bulletin said the documents submitted by campaigners meet formal legal requirements.
The group now has until Feb. 24, 2012, to collect the 100,000 signatures needed to call a popular vote on reintroducing the death penalty for murders involving sexual abuse, the announcement said.
Switzerland eliminated capital punishment from its criminal statutes in 1942. The last civilian to be executed in Switzerland was beheaded in 1940. The death penalty remained part of Switzerland's military law until 1992, though the last executions took place by firing squad in 1944.
Authorities have yet to examine whether the death penalty would be constitutionally legal and in line with Switzerland's international obligations, including the European Convention on Human Rights.
Government spokesman Andre Simonazzi said if parliament finds that capital punishment would breach the Swiss constitution or international treaties it can block the referendum from taking place.
The proposal to reinstate the death penalty has drawn criticism from all sides of the political spectrum and comes less than a year after Switzerland made headlines worldwide by voting to ban the construction of minarets.
A spokesman for human rights group Amnesty International in Switzerland, Daniel Graf, said reintroducing capital punishment would put Switzerland at odds with a general trend around the world to abolish the death penalty. The only country in Europe that still practices the death penalty is Belarus, he said.
"I don't think many people will support this proposal," said Graf. "In Switzerland, there is a broad consensus across party lines that the state shouldn't kill and must respect basic human rights."