The original question on the UU Leaders chat was: "Does a minister's Freedom of the Pulpit extend to the right of first refusal over non-member weddings" If you're just joining this blog, scroll down three posts and read them over to catch up.
So. Freedom of the Pulpit has nothing to do with this.
Control of Sacred Space has to do with this question only if there's the possibility that the activity or leader would reflect badly on the church or be seen as sacrilegious.
Minister's covenants of relationship with each other govern some of this but lay folks don't need to worry about them.
The essence of this issue, however is economic. Ministers get paid for doing weddings. Ministers who like the extra income, and the many who need the extra income want all the opportunities to do these weddings they can have. Organists often feel the same way. Because both ministers and organists are often poorly paid, they are often indulged in this little bit of protective behavior. So, lay folks, if your minister is demanding a right of first refusal for non-member weddings, the first thing to wonder is if you are paying this person well enough that they don't have to work weekends and evenings doing weddings. Then you can start negotiating.