When the Church Admin is creating the base Blue, Green, or Red years, they can determine sections they want to "lockdown" so that group leaders are not able to swap out those sections. When the admin clicks the lock, that section will have to be part of every group's curriculum that year.
For example, if a church's leadership decided that they wanted to make all groups use the Gospel Living section, the admin would click the lock for that section when setting up a base color year. The Group Leader will not be able to switch out that section for another.