IN THE AFTERMATH of the attempted Times Square bombing, Attorney General Eric H. Holder Jr. offered to work with Congress to craft legislation to give law enforcement officials more flexibility in questioning terrorism suspects before being forced to give Miranda warnings.

Nearly one year later, there is no legislation; the effort, the Obama administration says, was thwarted by Democrats who were squeamish about tampering with civil liberties. Instead, the FBI has acted on its own to give agents more leeway in such cases.

The FBI’s new ground rules build on a Supreme Court case that permits interrogations without Miranda warnings to thwart an imminent threat; the court said that information gathered during this relatively brief period — often just a matter of hours — may be used in court. The FBI, in a brief memorandum issued in October, has advised field agents to “ask any and all questions that are reasonably prompted by an immediate concern for the safety of the public . . . without advising the arrestee of his Miranda rights.” Once “public safety questions have been exhausted,” suspects must be read their rights.

The FBI memo makes accommodations for longer interrogations in “exceptional cases” in which agents try to “collect valuable and timely intelligence not related to any immediate threat.” Such agents must seek approval from their supervisors and, if possible, from FBI headquarters.

The move toward more flexibility is warranted, but such changes would be on sturdier legal ground with Congress on board. This unilateral approach also leaves too many questions unanswered and too many issues unaddressed. For example, should Miranda-less statements taken after the immediate public safety threat has been assessed and possibly defused be admissible in court? That is a debate worth having and one that should involve Congress.

And there are critical steps the administration cannot take without lawmakers’ approval. Federal rules, for example, require that a suspect be brought before a judge “without unnecessary delay” — usually within 24 to 48 hours. The FBI memo — as it must — instructs agents that “presentment of an arrestee may not be delayed simply to continue the interrogation, unless the defendant has timely waived prompt presentment.” But what if law enforcement and intelligence officials believe they need more time to lawfully extract additional information?

Congress and the administration should consider a rule change to allow a suspect to be questioned for a matter of days, rather than hours; this added measure of flexibility would come with a requirement that a federal judge be informed that the suspect was being questioned to ensure that the more malleable standards were not being abused. All interrogations would also be governed by domestic and international strictures against torture and cruel and inhumane treatment.