This dissertation explores the struggle in Canada over international boycott campaigns, providing a comparative analysis of Canadian solidarity movements which deploy economic practices of boycott, divestment, and sanctions (known collectively as "BDS") to target the policies of foreign country, specifically focusing on campaigns against apartheid South Africa and contemporary Israel. In particular, this study looks closely at the organized backlash to these campaigns, including the role of domestic lobbies and state-led propaganda campaigns, in an attempt to explain why the boycott campaign against South Africa appeared to be so successful, while the campaign against Israel has struggled to become popular. This analysis relies on original archival research, as well as interviews with both supporters and opponents of these boycott movements. It also provides a new theorization of BDS in terms of its political economic character, exploring the limits and possibilities of these forms of activism, both in terms of material economic impact (as per Marx) and their role in ideological struggle (as per Gramsci and Hall). This study identifies a number of factors which distinguish the pro-South Africa and pro-Israel lobbies, which have affected the ability of each lobby to articulate to common sense and build popular and state support. While the pro-South Africa lobby ultimately failed to counter the anti-apartheid movement, Israel's support within Canadian society has allowed its defenders to go further and deploy coercive measures against boycott supporters, narrowing the space for pro-Palestinian solidarity activism.