DOJ would have you think that a victory for it in United States v. Texas is necessary to ensure that liberal states won’t be able to get away with enacting copycat laws that “ban the sale of firearms for home protection … or prohibit independent corporate campaign advertising” in defiance of Supreme Court precedents. (See DOJ Brief at 41.) But that requires you to assume that this DOJ (and DOJs in other administrations) can be counted on to impartially protect constitutional rights recognized by the Supreme Court. Why would anyone imagine that this DOJ would, say, sue New York if it adopted a copycat scheme against firearms?
I pointed out yesterday that Congress has broad power that it has not exercised to authorize lawsuits by the United States to enforce abortion rights under Roe and Casey. I should also have emphasized that it has broad power to authorize lawsuits by private persons to enforce abortion rights under Roe and Casey—as well as other rights recognized by the Supreme Court—and to abrogate the traditional limits on equitable relief (something that section 1983 indisputably does not do). So in practice the best solution, if Congress sees fit to act, would be for Congress to confer on private parties the ability to protect their own interests and not depend on the political whims of DOJ.
In any event, my broader point remains: The federal body that has authority to decide whether the Texas Heartbeat Act poses a novel problem that warrants a novel remedy is Congress, not the executive branch and not the federal courts.