The issue is that there's a pretty sweeping power under regulation for the government, and if they're able to create this exemption presumably the power allows them to create other exemptions; it's not a limited exemption-making power. If as legislators we're approving the creation of a new tax that's supposed to have a policy objective, but government can create exemptions whenever it wants....
There's certainly an argument for some regulatory power to be able to tweak things, because I appreciate that something like this can have unintended consequences and we may not get everything right the first time. But here we're in a situation where the government has a very specific kind of exemption they want to create for this tax, and they're essentially not seeking to have that in the legislation or to have legislators approve that exemption, They're saying we're going to have this sweeping power that normally we might think is for tweaks and modifications in order to ensure that the new tax coheres with the policy objective, but by the way, we're already telling you we're going to use this to create a major new exemption. It raises the question of what other kinds of major new exemptions might be created for a tax that already has a number of what you can call loopholes—I appreciate that that's a more pejorative term—but certainly a lot of ways for people to avoid paying this tax.
Are there any other exemptions that are under discussion at this time for this tax? How can I have confidence as a legislator that government won't use this same regulatory power to create other significant exemptions to the tax after it's passed through Parliament?