Where is it illegal to own just one guinea pig?

In Switzerland it’s illegal to own just one Guinea pig

The Swiss are known for their historic commitment to neutrality, but they’ve taken a firm stand on one of the most important issues of our time: guinea pigs. Because guinea pigs are social creatures who grow lonesome without a friend, it’s illegal to own just one of them in Switzerland. The law was introduced in 2008 as part of a legislative effort to grant social rights to pets. Should one guinea pig depart this mortal coil and leave its companion alone — and its owner in potential legal trouble — rent-a-guinea-pig services have emerged as a temporary solution.

Guinea pigs aren’t the only pets afforded special status in Switzerland. Goldfish are also prohibited from being kept alone, cats must at least have access to a window where they can see their fellow felines prowling around, and, for a time, dog owners were required to take an obligatory training course with their pooch, although that law was repealed in 2016. For all this, Switzerland doesn’t have an official national animal — though both the country and the Alps in general are strongly associated with cows and Saint Bernards.