Obama ignored the law to free Bergdahl. Don’t expect the Senate to do much about it.

Senators are frustrated with President Barack Obama for ignoring a legal provision requiring the secretary of defense to notify Congress 30 days before releasing detainees from the U.S. military prison at Guantanamo Bay, Cuba.

And members of the Senate from both parties don’t really know what they can do about it.

The administration last week swapped five alleged enemy combatants in exchange for the freedom of Army Sgt. Bowe Bergdahl, who has been held captive in Afghanistan since 2009. But the Defense Department did not inform Congress until after the deal was done.

On Wednesday, senators from both parties — including the chairmen of the Senate committees responsible for oversight on national security and intelligence issues — suggested in Capitol Hill interviews that there was little they could do in response to the White House’s decision to ignore the letter of the law.

Obama announced the secret deal last Saturday during a ceremony with Bergdahl’s parents in the Rose Garden at the White House, nearly five years after Bergdahl went missing from his post in Afghanistan on June 30, 2009. Soldiers who served with him have accused him of being a “deserter,” though the circumstances of his departure remain murky. The Army intends to open an investigation into the details of his disappearance and capture.

The Obama administration has argued that the president acted within his constitutional authority, pointing to a signing statement Obama attached to a defense authorization bill last year containing the congressional notification requirement. In his statement, the president called the constitutionality of that requirement into question and said that, as commander in chief, he reserved the right to act outside the provisions of the law under certain “circumstances.”

Faced with questions on Wednesday about whether they believed the circumstances of Bergdahl’s release were constitutionally sound, top senators said they would withhold judgment.

“I’m not a court that’s going to decide whether or not under Article II the Commander in Chief has the power to move this quickly even though Congress says you’ve got to give a 30-day notice,” said Michigan Sen. Carl Levin, chairman of the Armed Services Committee. “It’s a legal issue, which is up to a court to resolve. I’m not going to resolve it.”

Levin acknowledged that Obama “did not comply with the requirement of the 30-day notice,” but he highlighted the signing statement as justification for the president’s action. “He put us on warning at that time,” Levin said. “On notice that he would act under his own constitutional powers if necessary. So he’s obviously decided that he has the power.”

California Democratic Sen. Dianne Feinstein, who chairs the Senate Intelligence Committee and has accused the administration of not following the law as well, said she was not considering legal recourse “at this time.”

Feinstein on Tuesday said she received a telephone call from national deputy security adviser Tony Blinken on Monday night apologizing for not notifying her of the swap. According to Feinstein, the top Obama aide called the lack of communication “an oversight.” Sen. Saxby Chambliss of Georgia, the top Republican on the Senate Intelligence Committee, said he received a similar call.

Senate Republicans, who are in the minority, also were finding themselves at a loss for viable legal options as controversy on the right over the legality of the swap grew.

“Unfortunately, given the makeup of the Senate right now and even in the near future, we’re quite limited in what we can do,” Florida Republican Sen. Marco Rubio told Yahoo News.

Rubio dismissed a question about whether impeachment was an option.

“I haven’t heard anyone seriously discuss that at this point. We need to learn more about this topic,” he said. “I’m certainly not calling for that at this point. It’s irrelevant because we wouldn’t have the votes in the Senate to even talk about stuff like that.”

Meanwhile, former Florida House Republican Rep. Allen West, whose name appears on the Republican National Committee straw poll of possible presidential nominees in 2016, called for the impeachment of Obama in an op-ed in the Washington Post on Wednesday.

Arizona Sen. John McCain, who spent five years as a prisoner of war and has been critical of the way Obama handled Bergdahl’s release, also conceded there were few options.

“What can they do, impeach him?” McCain said. “It’s a breakdown of trust between the legislature and the president of the United States.”

He added: “The law is not my problem. The law is the law, and that will be taken care of over time. What my problem is, is what these five people do, and it’s obvious they will return to the fight and put the lives of men and women in danger.”