“In general, no organization, including a church, may qualify for IRC [Internal Revenue Code] 501(c)(3) [tax-exempt] status if a substantial part of its activities is attempting to influence legislation (commonly known as lobbying)".
now prove a substantial part
What constitutes a substantial part to you? What percentage?
This church lost it's status:
Church loses tax-exempt status
Here's another:
http://www.nytimes.com/2007/09/18/nyregion/18grove.html
The Mormons should lose their tax exempt status over Prop 8. Mormons think that civil marriage is an earthly contract and celestial marriage performed in a church temple and is a sacred covenant( according to an article in the church magazine Ensign).
Temple marriages are not being threatened. This move is not religious, it is political. LDS crossed state lines to insert itself into CA politics. The Mormon Church should be stripped of its tax-exempt status.
If a church seems to operate for mostly nonreligious purposes (i.e., political work or personal profit), the IRS can revoke 501(c)(3) status.