Since concluding his presidential campaign in July, Vermont Sen. Bernie Sanders has been planning and raising money for Our Revolution, a new advocacy group, to continue championing the issues he ran on.

From a legal standpoint, the organization is aptly named, as its relationship with a sitting U.S. senator raises novel questions of law. Furthermore, a “revolution” literally means a circular motion, and the complex convergence of campaign finance, tax, and congressional ethics rules at play here will cause even the most experienced lawyers’ heads to spin. Other politicians looking to replicate this model are advised to retain a “yuuuge” army of attorneys.

According to its website, Our Revolution will operate as a nonprofit entity under Section 501(c)(4) of the tax code. An initial email and Facebook announcement indicated the group “will focus on three distinct areas of work: (1) … bringing millions of working people and young people into the political system. (2) … inspiring, recruiting and supporting progressive candidates across the entire spectrum of government — from school board to the U.S. Senate. (3) … educating the public about the most pressing issues confronting our nation and the bold solutions needed to address them.”

The organization’s website also indicates the group is supporting and opposing various state ballot initiatives.

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Often derided (unfairly) as “dark money groups” because they are not required to disclose their donors, 501(c)(4) organizations like Our Revolution are legally permitted to engage in all of these activities under current tax law. However, a sitting U.S. senator’s involvement in such a group is unusual and raises several knotty campaign finance and congressional ethics issues.

The campaign finance laws explicitly recognize only two types of “political committees” that may be “established, financed, maintained or controlled” by a federal candidate or elected official: a campaign committee and a leadership PAC. Both are subject to contribution limits and source prohibitions that generally do not apply to 501(c)(4) groups.

Any other type of entity that is established, financed, maintained, or controlled by a federal candidate or officeholder is also subject to federal contribution limits and prohibitions if it engages in any activity “in connection with an election for federal office,” certain federal election activities, or even activity in connection with state or local candidate elections.

Federal candidates and officeholders are subject to other restrictions if they raise money for a 501(c) organization whose “principal purpose” is to conduct certain voter registration, voter identification, get-out-the-vote, or “generic campaign” activities in connection with federal elections. Federal candidates and officeholders must also comply with a set of difficult-to-understand Federal Election Commission opinions if they raise money to support state ballot measures, as Our Revolution is doing.

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The congressional ethics rules impose another hurdle. House members must obtain prior Ethics Committee approval before fundraising for a 501(c)(4). The House Ethics Manual suggests that solicitations for such an organization, established or controlled by a House member, have never been approved. A 501(c)(4) may also not be used to support a House member’s official activity.

Over in the other chamber, the Senate Ethics Manual suggests that members of a senator’s staff may not have any formal role in an organization with an interest in legislation within the senator’s jurisdiction. However, the rule for involvement in such groups by senators themselves is unclear.

Aside from these special considerations related to a federal officeholder’s involvement, the general rules for operating 501(c)(4) entities are also challenging. Under Internal Revenue Service rules, such organizations may not be “primarily” engaged in political campaign activity and are also taxed for such activity. To avoid regulation by the FEC as a political committee, such organizations may not raise or spend more than $1,000 per year in connection with federal elections and have the “major purpose” of influencing such elections. Thus, 501(c)(4) organizations must carefully monitor the balance of their political and non-political spending and understand which activities fall into which bucket under the incongruous FEC and IRS rules.

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Because of these legal complexities and grey areas, the more conventional path for federal candidates and officeholders seeking to promote a political agenda other than their own elections has been to form leadership PACs, which have their own compliance challenges. As noted before, limits and prohibitions apply to leadership PAC contributions, as do disclosure requirements.

Under Section 527 of the tax code, leadership PACs must also comply with IRS rules that are the mirror image of those for 501(c)(4)s. Leadership PACs must be operated “primarily” for political purposes, and any activities that are not sufficiently political are taxable. Political causes, including ballot measures, that are not explicitly tied to candidate elections may or may not qualify as political activities under the IRS’s nebulous “facts and circumstances” test.

Up until now, Sanders has been a vocal champion of campaign finance reform. Time will tell whether such “reform” includes a simplification of the laws, and whether the legal minefield Our Revolution faces will cause him to “feel the burn.” In the meantime, politicians looking to operate 501(c)(4)s had better lawyer up.

Eric Wang is an attorney in the Election Law Practice Group at Wiley Rein LLP.