When it comes to congressional Republicans and gun reforms, Sen. Pat Toomey (R-Pa.) has stood out for supporting a new national background-check law. In fact, six years ago, when Barack Obama implored lawmakers to act in the wake of the Sandy Hook massacre, the Pennsylvania senator was the lead Republican sponsor on a bipartisan bill.

Toomey’s GOP brethren ultimately killed his proposal, but the senator earned plaudits for his efforts. Given Toomey’s ideology – he’s long been a very conservative Republican who, among other things, served as the president of the far-right Club for Growth – he was an unexpected ally for reform advocates.

But yesterday, we were reminded about the limits of Toomey’s approach to the issue. HuffPost reported:

On Monday, the Pennsylvania senator said he supported expanding background checks but rejected the idea of a ban on assault weapons or restrictions on magazine size. Toomey explained his reasoning to Fox News host Sandra Smith on Tuesday: The weapons are simply too popular. “They are extremely popular, so to ban an extremely popular firearm, I’m not going to support that, that would be an infringement on the rights of law-abiding citizens,” he said.

There are a couple of glaring problems with this. The first, as the HuffPost report noted, is that no one can say with any confidence just how “popular” assault weapons really are, since no one knows how many Americans have bought them: “The government isn’t allowed to collect that info and put it in a modern, searchable electronic database.”

The second is that the popularity of a deadly weapon hardly seems relevant under the circumstances. When policymakers banned lawn darts, they didn’t spend a whole lot of time studying market trends or sales data. They took steps to save lives regardless of the product’s popularity.

Indeed, we can take this a bit further. In some circles, heroin is, to borrow the senator’s words, “extremely popular,” too. And yet, I don’t see Toomey making an effort to make heroin readily available as a legal consumer product.