Prime Minister Justin Trudeau's point person on legalizing recreational pot was the prize guest at a Liberal Party fundraiser attended by a marijuana lobbying group at a Toronto law office that advises clients in the cannabis business.

The event last spring, which featured Bill Blair, the parliamentary secretary to the Justice Minister, appears to violate Liberal Party rules on political fundraisers and Mr. Trudeau's ethics guidelines that direct cabinet ministers and parliamentary secretaries to avoid an "appearance of preferential access."

The Liberal Party told The Globe and Mail on Monday night it will refund donations from representatives of the Cannabis Friendly Business Association (CFBA), although it denied any ethical breaches.

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"While the lobbying code is clear that such individuals may be able to attend grassroots fundraisers, these contributions are now in the process of being returned to avoid any appearance of conflict of interest," Liberal Party spokesman Braeden Caley said in an e-mail.

"The individuals associated with the organization you reference appear to have only registered with the lobbying commissioner on or after the date of the event itself, and therefore the party would not have been aware in advance of their activities."

Mr. Blair addressed the fundraiser at the law offices of Aird & Berlis LLP on April 28 – two months after Mr. Trudeau named him to work with a task force on new marijuana laws.

One of the law partners is a corporate secretary in a cannabis business, and another assisted a client doing a medical marijuana startup.

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The CFBA represents dispensary owners and cannabis farmers who want the federal government to allow storefront pot shops.

CFBA organizers Abi Roach and Jon Liedtke, a co-owner of the Higher Limits Cannabis Lounge in Windsor, Ont., lobbied and were photographed with Mr. Blair, a former Toronto police chief, at the $150-per-person fundraiser.

"I got 10 minutes of his time. I explained to him that the cannabis industry needs to stay independent and he said, 'Oh Abi, it's not about money,' and I just laughed, and I said, 'You don't think so, eh?'" said Ms. Roach, who operates Hotbox Café, a cannabis lounge in Toronto. "It was worth it because I got to speak to different people about our point of view about the cannabis industry. There was lot of people from the cannabis industry as well who were vying for his attention, more from the licensed producers' side, obviously, because they are more interested in lobbying than the independents are."

The presence of donors hoping to gain the ear of Mr. Blair appears to violate Mr. Trudeau's Open and Accountable Government ethics rules that state "there should be no preferential access, or appearance of preferential access" in exchange for political donations.

The fundraiser also appears to breach internal Liberal Party rules – held up by the party as evidence of due diligence – that say "there is a thorough process to ensure that the rules are followed – especially that no department stakeholder, lobbyist, or employees of lobbying firms are specially targeted for fundraising."

Ms. Roach told The Globe she "gets e-mails all the time" from the Liberals asking her to come to fundraisers, and no one vetted her for the April 28 event.

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"They took our money happily without question," Ms. Roach said. "If it was easier for people to speak to politicians, to explain their points of views without having to pay – I mean, there was no way to sit at this event, I was on my feet for four hours – I would rather to speak to a politician one-on-one in an office than have to pay."

Ms. Roach's organization is registered with the Office of the Commissioner of Lobbying in Ottawa as lobbying the departments of Justice, Finance, Health and Public Safety, and the Public Health Agency of Canada and Employment and Social Development.

Fundraising rules recently highlighted by Christina Topp, interim national director of the Liberal Party, say: "Once we receive a guest list prior to an event, we review it to determine if any individuals are registered lobbyists with active files associated with the relevant department and, if necessary, takes steps so the individual does not attend the event."

The Liberal Party said some people, who were members of the Liberal Party Victory Fund, paid $20 per ticket. Members of the Victory Fund pay a monthly donation up to a maximum of $1,500 annually and get special rates for party events. The party has been unwilling to provide a complete list of the people who were at the fundraiser but Mr. Caley said it was "well over 70 supporters in attendance."

The fundraiser was for Toronto Liberal MP Nathaniel Erskine-Smith, who favours decriminalization of marijuana and the idea of pardons for people convicted of pot offences.

Mr. Blair insisted he was not using his position to raise money for Mr. Erskine-Smith's riding association.

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"Honestly, I went there and I spoke on behalf of Nat as a parliamentary colleague. It wasn't about marijuana," Mr. Blair told The Globe. "Everyone talks to me about marijuana everywhere I go, but that wasn't why I was at the fundraiser. Nat is a colleague and a friend."

Mr. Erskine-Smith, Liberal MP for Beaches-East York, said to his recollection, most people at the April 28 fundraiser were his former colleagues at the law firm, constituents and local Liberal Party supporters.

He said he did not discuss marijuana at the event, adding that Mr. Blair happened to be the parliamentary secretary who was available.

Mr. Erskine-Smith said at the riding association level it would be very difficult to screen all attendees to determine whether they plan to lobby the headline guest.

He said the topic of the April 28 fundraiser was how Mr. Trudeau brought people of varied backgrounds into the Liberal fold.

Mr. Erskine-Smith said his riding association never advertised the event as an opportunity for lobbyists to talk to Mr. Blair on marijuana.

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One partner at Aird & Berlis, Richard Kimel, is corporate secretary for International Cannabis Corp., a licensed producer of recreational marijuana, as well as extracts, byproducts and industrial hemp in Uruguay. Mr. Kimel was not at the fundraiser.

The law firm also represented TheCannaCabana.com website, which promotes itself as a place where people can "gather and communicate without fear of repercussions for their choice of medication and recreation."

Another law partner, Donald Johnston, advised a medical marijuana startup as it registered, according to Aird & Berlis' website.

Aird & Berlis referred questions about the fundraiser to the Beaches-East York Liberal riding association, including whether it donated or rented the space for the event. The firm declined to discuss its work on the marijuana file. "Those matters are subject to solicitor and client confidentiality," managing partner Steven Zakem said in an e-mail.