HELENA — The commissioner of political practices ruled Thursday that one of his predecessors violated Montana campaign-practices laws when he signed a tax form as the treasurer of a political group while still in office.

But Commissioner Jonathan Motl said there is no way to seek penalties against former commissioner David Gallik. He can’t be impeached because he already has left office, and the one-year statute of limitations for enforcement already has passed, Motl said.

When Gallik was commissioner from May 2011 to January 2012, he signed an IRS 990 tax reform as the treasurer for the Council for a Sustainable America. The group was registered with the IRS to influence the selection or defeat of candidates for public office, and it had received $335,000 from the Democratic Governors Association.

Montana law prevents the commissioner from participating in any political activity or campaign while in office, Motl said.

Gallik denied being involved in political activity. The group had ceased operations in 2010— before he became commissioner — and he simply signed the final tax return, he said.

“This was just the final IRS document that the accountant says you’ve got to put in,” Gallik said. “If I didn’t file the forms, the IRS would have come after me.”

Motl said he accepted Gallik’s explanation, but it does not relieve him of taking an improper action.