I just used this last night.
My daughter is in a CCD class (Catholic classes)...now my DH is Catholic, I am Protestant and we go to both kinds of churches, but anyway...
Somebody called telling us about some useful information about CCD, and then said they were asking for more volunteers.
I said "I am sorry, I have enough Volunteering commitments and I cannot not take on anymore" (and besides, I am not Catholic and I volunteer at the Methodist Church)...
She said "If people don't Volunteer, it may become mandatory."
I said "I understand."
I should have said "Well, then it is not really volunteering anymore is it?"