Today, the NDP have backtracked a wee bit and have said that they would not be bound by a TransPacific Partnership [TPP] agreement negotiated by the Conservative government. I then tweeted that Westminster systems are unreliable. How so?
Remembering a piece one of my advisers wrote a while back, and then a friend built on, the basic idea is that the more veto gates in the process, the harder it is to change a policy. In Canada, there is only one key decision point (most of the time): the Prime Minister. With party discipline and a majority or a clever strategy for handling a minority situation, a new PM can completely flip policy from the previous PM.
In a Presidential system, any policy has to pass through two or more veto points, such as the President and a legislature or even two houses of a legislature, so passing new legislation or radically revising adherence to a treaty is much more difficult. Not impossible, but harder.
In non-Westminster parliaments, proportional representation tends to lead to multiple parties in coalition, which means bargaining that is less likely to be undone after an election. Yes, a completely different set of parties can come in, but often there are parties that do not leave. For much, although not all, of Germany's post-war history, the FDP was junior partner with either the Christian Democrats or the Social Democrats. Also, as some on twitter noted, there are patterns of more consensual power-sharing so that international agreements are vetted not just by those in the coalition. Consensual is never a term folks use to describe confrontational government in British-style parliaments.
Anyhow, this basic set of differences among democracies make some more credible and reliable than others. And that means that what the NDP might be doing is problematic but entirely predictable.
Oh, and another reason for me to vote against the NDP--I am not a fan of protectionism.