Last week, Yakima Bishop Joseph Tyson sent a letter to pastors in 41 parishes asking that they announce a special collection at upcoming services that would go to Preserve Marriage Washington, which is opposed to same-sex marriage.
The group forced a vote with Referendum 74, which asks voters to either approve or reject the law passed earlier this year that allows same-sex marriage in the state.
That law is on hold pending a November vote.
The diocese's chief of staff, Monsignor Robert Siler, said Tuesday that the expected collection date was set for Sept. 8-9.
But Lori Anderson, a spokeswoman for the state's Public Disclosure Commission, said no organization can be an intermediary for a contribution.
The church can hand out envelopes at Mass, but a member of Preserve Washington has to be on hand to collect them, or parishioners must send them in individually, she said.
Anderson said the restrictions stem from Initiative 134, which voters passed in 1992 to regulate political contributions and campaign spending.
Siler said the diocese coordinated its efforts with the Washington state Catholic Conference.
"As far as I know, the procedures we sent to the parishes meet the requirement of state law," he said, noting that the envelopes are preaddressed to the campaign.
"We're not collecting and counting money," he said. "We're just collecting envelopes and forwarding them."
Anderson said that even so, what the church is proposing to do is what federal laws refer to as "bundling," and that isn't allowed under state law.
Anderson said PDC officials would be reaching out to church officials in the coming days.
"We just want to make sure they understand what they can and can't do," she said.
"Under state law, no one can be an intermediary for a contribution," Anderson said. "It doesn't matter if it's a loose pile of money or if each is in a little envelope."
Sister Sharon Park, executive director of the Washington state Catholic Conference, said she couldn't comment until she had talked with the PDC.
"It's hard to say anything without knowing what they are talking about," she said.
"If we need to amend our procedures, we will," Siler said.