On the eve of the first state court consumer class action trial over Merck’s Vioxx painkiller, the federal judge overseeing the Vioxx federal multidistrict litigation issued a rare All Writs Act injunction barring plaintiffs from “double-dipping” in the state case.

Monday’s decision by New Orleans federal district court judge Eldon Fallon effectively bars counsel for a class of Missouri consumers from presenting their key damages expert at trial next month. “We are reviewing Judge Fallon’s order and considering our options with respect to appellate review and what it means in terms of our damages case,” said co-lead class counsel Patrick Stueve of Stueve Siegel Hanson.

The plaintiffs’ expert witness has said that damages in the state case include all expenditures statewide on the drug, which was recalled in 2005; Judge Fallon concluded that the claims as construed by the expert would incorporate damages already covered under two earlier Vioxx settlements–the $4.85 billion personal injury settlement in 2007 and the $80 million third-party payors settlement in 2009. The judge cited the rarely used All Writs Act, which permits federal judges to interfere in state court proceedings on a limited basis to protect the court’s judgments.

In a sign of the importance of the trial, which is set to begin May 21 in Jackson County circuit court, Merck confirmed that it has tapped Philip Beck of Bartlit Beck Herman Palenchar & Scott as lead trial counsel. Beck and his colleagues tried many of the original Vioxx bellwether personal injury suits in 2005-2006. In addition to Beck, partners Brian Prestes, Adam Hoeflich, and Mark Ouweleen were admitted to the state court late last week. (Beck could not be reached at press time.)

Judge Fallon’s ruling comes four weeks after the Missouri state court judge, Marco Roldan, rejected Merck’s summary judgment motion, sending the case hurtling towards trial. This is the sixth and last state consumer class action against Merck over its sales of Vioxx; five other state cases have been either dismissed, denied certification, or decertified.

Skadden, Arps, Slate, Meagher & Flom’s John Beisner briefed the All Writs Act motion for Merck along with Williams & Connolly’s Douglas Marvin. (Most recently, in February, Beisner convinced a Kentucky state appeals court to decertify a similar consumer class action, as we reported.) Several other federal consumer class actions are still pending before Judge Fallon in the MDL; he has not ruled on certification yet.

In its motion, Merck argued that the state class’s purportedly overbroad damages claim, along with the state court judge’s recent decision allowing the expert, would harm not just Merck but the integrity of the MDL process and “threaten an explosion of new litigation by reopening all of the resolved” third-party payor cases.

Class counsel, echoing the state court judge’s summary judgment ruling, countered that the All Writs injunction was unnecessary, because the the MDL claimants “are not class members and, should one assert a claim, it can be handled as a matter of post-judgment claims administration in [the Missouri case], if and after the plaintiffs prevail at trial.”

“Merck is asking this Court to improperly hear an appeal of substantive state-law issues that have been decided by the Missouri state courts, for the purpose of derailing the first bellwether trial of Vioxx consumer class cases,” wrote Stueve Siegel and and Gray, Ritter & Graham in their April 3 brief.

Merck was originally represented in the Missouri case by Stinson Morrison Hecker; that firm was replaced by Bryan Cave and St. Louis partner Stephen Strauss a few years back as local counsel. Skadden’s Beisner was brought on board in 2006, just prior to certification, and is playing a coordinating role nationally. Dechert’s Ben Barnett came in in 2010 to handle discovery in the state case.

“Judge Fallon appropriately ruled that the plaintiffs in the Plubell case cannot seek to recover Vioxx payments made by personal injury claimants and third-party payors with whom the company previously settled in the federal multi-district litigation,” Merck said in a prepared statement. “The company is prepared to vigorously defend itself in the Plubell trial.”