The National Association of Manufacturers is suing the Clerk of the House and Secretary of the Senate over a disclosure provision in the lobbying reform law that the group says violates its constitutional rights.

The association also is seeking a preliminary injunction to block enforcement of the new requirement, NAM President John Engler said at a Wednesday morning press conference announcing the suit.

Engler said the provision “strikes at the heart of our First Amendment freedoms.”

At issue is a little-noticed piece of the Honest Leadership and Open Government Act that its authors said was aimed at shining light on “stealth lobbying coalitions,” groups that exist only on paper and whose financial backers remain in the shadows.

The provision requires coalitions to disclose any organization that contributes $5,000 per quarter and actively participates in shaping the lobbying campaign.

But unlike earlier proposals, the language of the final reform bill did not exempt established trade associations from the rule, meaning they could be forced to disclose their membership lists.

Groups found not to be complying with the new disclosure rules could face criminal penalties.

NAM officials, who filed the suit today in the U.S. District Court for the District of Columbia, said they hope to win an injunction before the first quarterly reports under the new rule are due in April.

“You can’t undisclose your members,” Engler said.

The association has hired Jan Baran and Tom Kirby, partners at Wiley Rein, to assist with the suit.