Write concern in mongodb All,

Lets say devoper sets the write concern as Majority in MongoDB

As a DBA can i have the access to change the write concern of whole cluster or only the developers has the rights to do through coding ?

In replica sets we can do the change through conf settings but i beleive it wouldn't override the default one
Write concern can be set differently for every DML operation and that overrides the default write concern value. So, if default value is majority, developer can choose w:0 or even w:all for update operation, if he or she wants to do so.