MP Ari Koponen was found guilty of illicit fundraising through his Brother Christmas association.
Eastern Uusimaa District Court fined him just over 1,000 euros on Tuesday for improper fundraising.
The court ruled that he violated fundraising laws over the first seven months of 2017. During that time his group received about 180,000 euros in donations, of which only 20,000 euros were in return for a product.
The group distributed buttons and bracelets in exchange for donations of 10-25 euros. The court found that the group should have had a permit for this activity under the terms of the Fundraising Act.
The court ruled that the statute of limitations had already run out on another case of suspected fundraising by Koponen in 2016. That collection, under the name of his personal company, raised 24,000 euros.
The court declared that Koponen was aware that he should have had a permit for the fund drives.
The prosecutor had sought much stiffer fines for Koponen and other members of the association's board.
Koponen claims negative publicity "harmed his health"
Koponen meanwhile argued that he should not be punished at all because the publicity around the case had been harmful to his health.
The court dismissed this, noting that any fundraising drive is an open public activity that may result in negative publicity.
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It decided not to punish the other board members, noting that in practice Koponen was responsible for the organisation's operations. All the defendants had denied breaking any laws.
In a Facebook post on Tuesday afternoon, Koponen decried the ruling as unfair and unreasonable. He pledged to carry on his Brother Christmas activities alongside his parliamentary duties.
Koponen was elected to Parliament on the nationalist Finns Party ticket last spring.