Proposed by then-Senator Lyndon B. Johnson, the amendment affects churches and other nonprofit organizations with 501(c)(3) tax exemptions. In recent years the Alliance Defending Freedom has attempted to challenge the Johnson Amendment through the Pulpit Freedom Initiative, which urges church pastors to violate the statute in protest. The ADF contends that the amendment violates First Amendment rights.
Organizations recognized under Section 501(c)(3) of the U.S. tax code are subject to limits or absolute prohibitions on engaging in political activities and risk loss of tax exempt status if violated. Specifically, they are prohibited from conducting political campaign activities to intervene in elections to public office.
IRS explanation of the statute
The Internal Revenue Service website elaborates upon this prohibition as follows: 
Under the Internal Revenue Code, all section 501(c)(3) organizations are absolutely prohibited from directly or indirectly participating in, or intervening in, any political campaign on behalf of (or in opposition to) any candidate for elective public office. Contributions to political campaign funds or public statements of position (verbal or written) made on behalf of the organization in favor of or in opposition to any candidate for public office clearly violate the prohibition against political campaign activity. Violating this prohibition may result in denial or revocation of tax-exempt status and the imposition of certain excise taxes.
Certain activities or expenditures may not be prohibited depending on the facts and circumstances. For example, certain voter education activities (including presenting public forums and publishing voter education guides) conducted in a non-partisan manner do not constitute prohibited political campaign activity. In addition, other activities intended to encourage people to participate in the electoral process, such as voter registration and get-out-the-vote drives, would not be prohibited political campaign activity if conducted in a non-partisan manner.
On the other hand, voter education or registration activities with evidence of bias that (a) would favor one candidate over another; (b) oppose a candidate in some manner; or (c) have the effect of favoring a candidate or group of candidates, will constitute prohibited participation or intervention.
The Internal Revenue Service provides resources to exempt organizations and the public to help them understand the prohibition. As part of its examination program, the IRS also monitors whether organizations are complying with the prohibition.
- Stanley, Erik; Lynn, Barry W. (September 25, 2008). "Tax laws and religious speech: what the Constitution says". Los Angeles Times. Retrieved September 14, 2010.
- Berlinerblau, Jacques (2011-10-05). "Where does church end and state begin? - Georgetown/On Faith". The Washington Post. Retrieved 2011-12-26.
- Eyes wide shut: The ambiguous "political activity" prohibition and its effects on 501(c)(3) organizations, Houston Business and Tax Journal, by Amelia Elacqua, 2008, page 119 and 141, referenced February 16, 2012
- "The Restriction of Political Campaign Intervention by Section 501(c)(3) Tax-Exempt Organizations". Irs.gov. 2012-08-14. Archived from the original on 2 December 2010. Retrieved 2012-09-09.
- Dorf, Michael C. (6 Oct 2008). "Why the Constitution Neither Protects Nor Forbids Tax Subsidies for Politicking from the Pulpit, And Why Both Liberals and Conservatives May be on the Wrong Side of this Issue". Findlaw.