term:

Permissive

permissive adj

1 : based on or having permission [ occupancy] [a user of the vehicle]
2 : granting permission or discretion (as to the court) [a statute]
3 : not compulsory: as
a : allowed or made under a standard, rule, or provision that permits discretion or an option see also permissive intervention at intervention permissive presumption at presumption compare compulsory
b : allowed under modern rules of civil procedure although not arising from the same transaction or occurrence as the one at issue in the original claim [a counterclaim] see also permissive joinder at joinder
per·mis·sive·ly adv

per·mis·sive·ness n