Washington’s Supreme Court strongly reinforced the longstanding principle of political financial transparency this month. However, supporters of public disclosure law must remain on alert. The same 5-4 decision that endorses the public’s right to information also shows an opening for a challenge to the accountability mechanism that makes the system function.

With the fresh ruling that political transparency requirements don’t violate the Constitutional right of free speech, Attorney General Bob Ferguson must carefully preserve the state’s full power to punish offenders. Political cycles run faster than the courts can fairly operate, so keeping future campaigns honest requires a penalty for breaking rules that outweighs the benefits of winning an election. Otherwise, big-money interests can break rules and shrug at the consequences as the cost of doing business.

In 2013, the Grocery Manufacturers Association blatantly attempted to conceal the donors — PepsiCo, Nestle and Coca-Cola, among others — that spent millions on the campaign against Initiative 522. That proposal would have given Washington the nation’s first requirement to label all foods made with genetically-modified ingredients. It lost by an extremely tight margin, 51.1% to 48.9%. Fewer than 40,000 votes out of 1.75 million statewide made the difference.

“It leads one to wonder: if full disclosure had been made, would that have made the difference?” said David Ammons, the longtime Associated Press reporter who now chairs the state Public Disclosure Commission. “They wanted it to fail, and it did fail by a whisper. That’s the power of money.”

Without registering as a political committee until the state filed a lawsuit, the trade group funneled $11 million into the “No on 522” effort. A judge found the scheme so egregious, she imposed a $6 million fine, then tripled it for intentionally breaking state law. The $18 million penalty is the largest for a campaign-finance violation in American history and shows future campaigns Washington rigorously enforces its gold-standard disclosure laws.

While the court rightly upheld the power to triple punitive damages for deliberate transgressions, the mandate also requires lower courts to reexamine the dollar amount involved. Both the state and U.S. constitutions prohibit “excessive fines.” As eye-popping as the total penalty in this case was, it’s in line with the size of the chicanery. State courts should restore the full fine. Ferguson must establish a thorough legal rationale that can withstand scrutiny if the issue moves into a federal courtroom. The U.S. Supreme Court cleared a path for huge corporate spending in elections with the 2010 Citizens United ruling, and the high court’s membership has grown more conservative since then.

Washington’s capacity to enforce campaign-finance laws in proportion to the money involved in elections must be preserved. A 1974 Washington Supreme Court opinion quoted by Justice Mary Yu in the Grocery Manufacturers Association case got it right: “The right to receive information is the fundamental counterpart of the right to free speech.” The public has an absolute right to know who’s behind every campaign.