Q: There is a kosher pizza store in town. Can the owner restrain me from opening a competing store?

A: This issue of hasagas gevul (interfering in another’s business) is addressed in Bava Basra 21b. Tannaim dispute whether one can prevent someone from opening a competing business adjacent to his. Most Rishonim rule that the first tradesman cannot prevent him unless the potential competitor lives and pays taxes in another city (C.M. 156:5). Nowadays, due to the different circumstances of commerce, we usually cannot prevent a competitor even from a different city. However, the Gemara introduces the concept of pasakta l’chiyusi (you cut off my livelihood). If the newcomer threatens to cut off the income of the original tradesman entirely, many rule that he has the right to restrain the competitor (Pischei Teshuva 156:3; Igros Moshe C.M. #38). Furthermore, he is prohibited to compete in an unfair manner, such as by selling below cost (Erech Shai 228:18). Thus, the ability of the pizza store owner to restrain you from opening is very restricted. However, it is meritorious not to encroach upon another’s livelihood (Chavas Yair #42).