A sweeping directive by the Ministry of Agriculture is prohibiting the entry into Israel of personal sets of four species for the Sukkot holiday without prior coordination between people and the ministry's Plant Protection and Inspection Services. The ministry is allowing people to bring in personal etrogs (citrons).
As is the case with all plants and their products, the purpose of the directive is to prevent the introduction of pests and pathogens to plants, such as insects, mites, nematodes, fungi, bacteria and viruses, that otherwise don't exist here, which could lead to the destruction of entire parts of the agricultural sector. It is a common practice around the world.