GRAND RAPIDS, Mich. (WOOD) — Michigan’s Proposal 2 has been challenged in federal court just hours after it passed.

The proposal, which passed with more than 80% of the vote, bans regulated utilities and companies with more than $250,000 a year in state or local contracts from donating to local candidates. It also tightens disclosure rules for political communications supporting or opposing a candidate.

The Mackinac Center, a conservative think tank, filed a lawsuit Tuesday night in the U.S. District Court for the Western District of Michigan arguing those disclosure rules violate First Amendment free speech protections and 14th Amendment protections against enforcement of vague laws. It names Michigan Secretary of State and Gov.-elect Jocelyn Benson and Attorney General Dana Nessel as defendants.

Proposal 2 contains a section regulating “electioneering communications expenditures.” That section would require entities that spend more than $5,000 in a year on political communications with certain conditions to file a report that could include information about donor identities.

The lawsuit argues the definition in the proposal is loose enough that it might encompass the Mackinac Center’s own communications, even though the group cannot legally make partisan statements or endorse candidates as a 501(c)(3) nonprofit.

It suggests, for example, that the Mackinac Center’s bimonthly impact magazine could fall under the proposal’s purview because it often mentions political candidates, like those who attend Mackinac Center events, and costs more than $5,000 to produce.

Requiring the organization “to continuously track its spending for all public communications that directly or indirectly refer to a candidate for office during the relevant period to determine when it exceeds the $5,000 aggregate threshold for reporting” would require the organization “to divert significant resources to this task that would otherwise have been used to further Mackinac’s mission,” the lawsuit alleges.

It also argues it is unclear whether the Mackinac Center would qualify as a “committee” under the proposal, which requires some groups that spends or receives more than $500 “for the purpose of influencing voters” to register as one. If it does, it would need to disclose its donors’ identities, which the lawsuit says would likely lead some donors to withdraw their support.

“The reporting requirements burden Mackinac’s ability to engage in constitutionally protected speech by imposing onerous costs on Mackinac and exposing it and its supporters to harassment,” the lawsuit says. “This creates an impermissible chilling effect on Mackinac’s speech and association.”

Proposal 2 includes a severance position, meaning a portion could be challenged in court and fail, and the rest would survive.