The Supreme Court of Canada has struck down a Ford government law that restricted political advertising by third parties, such as unions, in the year ahead of a scheduled election campaign.

The top court ruled in a 5-4 decision that the law allowed for political parties’ ads to “drown out” those of third-party groups, infringing on citizens' right to meaningfully participate in the democratic process.

“The information available to voters in Ontario in the year before an election must include the interests, voices and views of different citizens and parties,” reads the majority decision written by Justice Andromache Karakatsanis.