Yet the court offered no clear indication that it was prepared to order Ashcroft and Mueller removed from a suit filed by Javaid Iqbal, a Pakistani Muslim who spent nearly six months in solitary confinement in New York in 2002.
Iqbal, since deported from the United States, says Ashcroft, Mueller and others implemented a policy of confining detainees in highly restrictive conditions because of their religious beliefs or race.
"The question here is, who is responsible?" said Alexander Reinert, Iqbal's Yonkers, N.Y.-based lawyer.
Solicitor General Gregory Garre argued on behalf of Ashcroft and Mueller that nothing in Iqbal's complaint ties the allegedly discriminatory acts of lower-level officials to his clients.
The case will help determine when Cabinet officers and other high-ranking officials can be sued over allegations that lower-level government workers have violated people's civil rights.
A federal appeals court said the lawsuit could proceed, but the Bush administration says the high-ranking officials should be dismissed from the suit because Iqbal lacks evidence that they intended or condoned the harsh treatment.