given that these are in fact just two synonyms "permission" is simply the plain speak variant for "leave" as used legal texts (as in "being given leave to appeal" for example), I would be tempted to just use one word (допуштење. одобрење ...) or rephrase in a way to use a verb (допустити, одобрити ...)


What does "You've been granted leave to appeal against the decision." mean?

The phrase “granted leave” literally means “permission” (“leave” here means “freedom”).
Therefore, congratulations. Your right to appeal has been granted by the court. “Granted” means “allowed.”

It means that some judicial or administrative entity has decided against you, and you have been given permission to appeal that decision to a higher tribunal (such as an appellate court).

“Leave” as a noun can mean
-- To be given permission
-- Allowed to be absent from duty (In the army)
In this sentence, the person has been granted permission to appeal a decision that has been made.
...

https://www.quora.com/What-does-Youve-been-granted-leave-to-...

"being given leave to appeal"
=

добити допуштење суда за подношење жалбе

суд је допустио подношење жалбе на одлуку

суд је одобрио право жалбе

итд...

I don't see any point in trying to reproduce in Serbian two synonyms, especially that as far as I know there isn't any "special legal term" for allowing an appeal that only lawyers can understand and is puzzling to anyone else - it's simply "жалбе је допуштена" / "право на жалбу је одобрено".

All parties should prepare for the hearing to proceed on the possible basis that permission or leave will be granted by the Court for the admission of the psychologist’s report and evidence.

Све стране у спору треба да своје припреме за главну расправу заснују на могућности да суд допусти да извештај и исказ психолога буду прихваћени (/у смислу: укључени у поступак)




--------------------------------------------------
Note added at 27 days (2018-08-16 02:57:42 GMT) Post-grading
--------------------------------------------------

"жалба је допуштена"