"Special permission" refers to the authorization or approval given to someone to do something out of the ordinary or beyond the usual rules or restrictions. Full definition
She had me come in right away and she got special permission from my insurance company to see my twins due to the problem. (twiniversity.com)
Third - graders have gotten special permission from their parents to stay after school. (americanradioworks.org)
The decision of whom they would invite was made when the invitation was written and asking for special permission for you baby / children can make things uncomfortable. (thespruce.com)