"But as you need a permit, it's still not a right. You can't license a"right""
...nor can you tax it. But try telling that to the NFA Branch, or to the Excise Tax collectors, or even the state sales tax divisions.
IMO, sales and excise taxes on guns and ammunition are as Constitutional as poll taxes or taxes on churches. (actually, of those I mentioned, the tax exempt status of churches is the only one that's on shaky ground. If churches have a 1A right to avoid taxation, why don't newspapers have the same right?)