Ius singulare
In Roman law, ius singulare (Latin, "singular law") was a special law that applied to a certain class of persons, such as soldiers or minors, or to an individual, in contrast to ius commune civium Romanorum, the law in common to all Roman citizens. In effect, ius singulare was "a technique for incorporating new rules without having to change the old ones." Ius singulare generally conferred an advantage to the group or individual singled out.