Under the current ruleset the panel is clearly not an NPC, The CP are also allowed to build within the pd and can make lines/restrictions as they wish, including KOS, They can lock the front doors if they really wanted to be assholes as well.
also, if this bothers you, go mayor and deal with it lol, Unless the mayor has an issue with it it's between the CP to do with their base as they wish, the panel is a privilege not a right which is why the mayor has a dedicated mechanic to lock this.