The Senate has passed the government’s signature affordability legislation but not before putting an expiry date on controversial provisions that exempt political parties from privacy laws.

In a close vote on Thursday night, senators approved an amendment from Senator Pierre J. Dalphond that would automatically repeal the privacy changes three years after Bill C-4 becomes law. Twenty-eight senators voted in approval, 24 opposed and eight abstained.

The so-called sunset clause was the only one of the three amendments at third reading debate that won approval.

Another amendment to remove the entire privacy section was easily defeated.

The bill now moves to the House, which must decide on whether to accept or reject the changes. If rejected, the bill would return to the Upper Chamber and senators would vote to either insist on their changes or scrap them.

It’s rare for the Senate to insist on amendments after being rebuked by the House.

Bill C-4 cuts the lowest tax rate from 15 to 14 per cent and eliminates the GST on new homes priced up to $1 million for first-time buyers.

But it also includes a section to exempt political parties from provincial privacy laws.

Political parties are already exempt from federal privacy laws.

Bill C-4 only requires parties to come up with their own privacy policies and have one annual meeting with the Chief Electoral Officer.

Parties that fail to comply with their own privacy policies could face administrative monetary penalties from the Commissioner of Canadian Elections.

The bill also provides retroactive exemptions for the parties back to 2000. This is likely because of a 2024 decision by B.C.’s Supreme Court that ruled that the federal Liberal party had to comply with the province’s privacy law.

Canada’s three major political parties have lined up in support of the bill, defending the changes as a way to exert federal jurisdiction and claiming that political parties are unique entities that should be treated differently than corporations.

They argued C-4 aims to create a single, national privacy regime and clarifies that jurisdiction over federal political parties lands with Parliament and not provincial legislatures.

Critics have countered that the issue isn’t jurisdiction but instead the lack of a strong federal regime.

It’s very rare for the Senate to make changes to a government bill on tax or monetary measures. One of the most famous examples came in 1990 when the Upper Chamber initially blocked legislation to implement the GST.

Then-prime minister Brian Mulroney invoked a rarely used section of the Constitution to appoint eight additional senators to pass the bill.

Bill C-4 passed third reading in the House in December on division, with Green Leader Elizabeth May asking for her opposition to be noted.

But May supported the bill at second reading, where it won unanimous support from the House.