A quick definition of jus in personam:

Jus in personam means the right to take legal action against a specific person to make them do something they are obligated to do. It is also called jura in personam. A right is something that is fair and just, like the right to freedom or the right to own property. Some rights are absolute, which means they cannot be taken away, while others are conditional, depending on certain circumstances. There are also different types of rights, like civil rights, conjugal rights, and patent rights.