Both the plaintiffs and the defendants in a US lawsuit challenging the government’s right to fund research using human embryonic stem cells filed court documents declining to consent to another party – the University of California – from joining the case.

Earlier this week, the University of California petitioned the court to participate in the case as a so-called intervener – meaning it would be neither a plaintiff nor a defendant, but would file in support of the government’s position in the case. The court asked the plaintiffs (adult stem cell researchers James Sherley and Theresa Deisher) and the defendants (the National Institutes of Health and the Department of Health and Human Services) to reply to the request today before it makes a decision.

In their response (PDF here), the plaintiffs argued that UC has not demonstrated “exceptional and imperative reasons” for intervening. They also state that “the Government will adequately represent whatever interests the Regents may have in this case.”

The government – aka the defendants – seems to agree. UC has a “valuable and significant perspective to offer this Court,” says their court filing (PDF here). “We decline to consent to intervention, however, because the federal government defendants adequately represent the University’s interests in this appeal.”

Because UC’s legal interests don’t differ from those of any other university, “Allowing intervention by the University could therefore lead to further requests to intervene by numerous nonparties who also can demonstrate irreparable harm that would stem from the district court’s preliminary injunction” – something which could complicate the proceedings. Instead, the document says, UC would do better to position itself as an “amicus curiae,” or “friend of the court.”

An amicus request by a stem cell research lobbying group filed earlier this month was declined by district court judge Royce Lamberth. The current proceedings, however, are taking place in the context of an appeals court. The appeals court is set to hear oral arguments on Monday about whether it should lift the temporarary stay it imposed on a district court injunction, which, in turn, banned federal funding for human embryonic stem cell research while the lawsuit is decided [see Case History].