The Department of Justice wants to know whether allowing T-Mobile and Sprint to merge would raise prices for customers of other wireless carriers, according to Reuters. The department is reportedly reaching out to MVNOs — mobile carriers that rent airwaves from the major networks — to get their thoughts on the effects of the merger.

That’s an important question in this case, because — as Reuters points out — T-Mobile and Sprint are the primary companies that rent out their network. Google’s Project Fi, for instance, uses the networks of both T-Mobile and Sprint in order to provide thorough coverage to customers. Allowing the two carriers to combine would substantially reduce competition, allowing the new company to charge more, which would lead to higher prices for consumers.

The Justice Department’s actions here are standard practice for now; according to the report, this isn’t any sort of deeper investigation that would hint at government opposition to the merger. But it’s an important question for the government to probe, since US antitrust law is largely based on consumer pricing.

If the DoJ believes the merger will raise prices more than it would reduce them, it would have grounds to oppose their combination — or at least put restrictions on it. And while the Trump administration is generally pro-business, the Justice Department’s attempt to block the AT&T–Time Warner merger shows that it isn’t opposed to shutting down a major deal.