(Bloomberg) — Outgoing House Oversight and Government Reform Chairman Darrell Issa issued a fresh subpoena against the Obama administration. Yes, yes, skepticism is in order. Darrell Issa subpoenaed the Treasury Department? Again? He's been draining the toner drawer with those sorts of requests for years.

This one's a little different. Issa is asking Treasury to turn over "all documents related to the development of the 36B regulation," i.e. the IRS rule that allowed residents of states that did not set up their own Patient Protection and Affordable Care Act exchanges to receive subsidies anyway. As Cato's Michael Cannon points out — with some personal interest — it's basically a Halbig subpoena. Halbig v. Burwell, the lawsuit against the IRS rule, won out in the D.C. circuit this July, but is widely expected to be cut down now that the whole circuit has gone en banc to review the prior, positive ruling.

For Cannon, who helped bring the case forward, and for the many Republicans who see Halbig as an PPACA-killer, this was an injustice that might have been prevented had the investigators been able to peer more closely into the IRS's process. In February, the Ways and Means Committee's oversight team produced a report, based on what it could read privately and suss out in public hearings, that accused the Treasury of slapdash rule-making. The IRS appeared to "[impute] congressional intent from bills that did not and could not pass the Congress as a whole," a fact that so shocked the investigators (and might have shocked judges who got the case) that they underlined it.