With Congress back in session, Montana Sens. Max Baucus and Jon Tester will soon consider whether to adopt new provisions in a defense-spending bill allowing Guantanamo Bay detainees to be transferred to the U.S. for trial by federal courts.

After years of passing restrictions on such transfers, these new provisions, proposed as part of the 2014 National Defense Authorization Act (NDAA), are the first sign of any significant movement in Congress toward bringing the deeply flawed military commissions system at Guantanamo to an end.

When President Barack Obama took office in 2009, there was bipartisan support for closing Guantanamo. Yet only a few months into his first term, the momentum shifted, and Congress passed the first in a series of restrictions on the transfer of detainees to the U.S.

A common refrain of the proponents of transfer restrictions was that accused terrorists do not belong inside the U.S., or at least not in any particular member’s congressional district.

But those who express such concerns should understand that many people convicted of serious terrorism offenses are already locked up in U.S. federal prisons, including Omar Abdel-Rahman, the “blind sheikh” and Ramzi Yousef, both organizers of the 1993 World Trade Center bombing; Zacarias Moussaoui, one of the Sept. 11 plotters; Richard Reid, the “shoe-bomber,” Umar Abdulmutallab, the 2009 Christmas Day “underwear bomber” and Faisal Shahzad, the 2010 “Times Square bomber,” to name a few.

Notable domestic offenders are also incarcerated in federal prisons, such as Eric Rudolph, bomber of the 1996 Summer Olympics in Atlanta; Terry Nichols, co-conspirator in the Oklahoma City bombing; and “Unabomber” Theodore Kaczynski of Montana.

All of these individuals were convicted in federal courts and serving life sentences in the Administrative Maximum Facility in Florence, Colo. — the only federal supermax prison in the U.S. No inmate has ever come close to escaping from this prison. The fact is that the federal court system — while not without its own flaws — has been far more effective at trying terrorist suspects in accordance with fair trial rights than the military commissions at Guantanamo.

Since Sept. 11, there have been hundreds of terrorism prosecutions in federal court, while in the military commissions there have been only seven. And of those seven convictions, two have been overturned on appeal.

It is somewhat surprising that there have been so few cases tried in the military commissions when you consider that the entire system was set up to obtain convictions — not fair trials — complete with judges and jury pools hand-picked by the Defense Department, special procedural rules to admit evidence inadmissible in civilian courts, and even certain evidence obtained by coercion — long understood not only to be unlawful but also inherently unreliable.

Yet even these convictions are vulnerable, since in constructing the military commission system Congress and the president overreached. In overturning the only two convictions obtained by trial (the others have been by plea bargain), the D.C. appeals court upheld the requirement of US law that military commissions may only prosecute war crimes. The charges the court rejected — providing material support for terrorism, and conspiracy — have never been recognized as violations of the laws of war.

But they can and have been used extensively — some would say too extensively — to try accused terrorism suspects in civilian courts. However, these charges are both crimes under federal law that can be prosecuted in US courts.

Those Guantanamo detainees who do not face war crimes charges cannot be tried in military commissions at all. But justice is certainly not served by abandoning trials altogether and holding the men indefinitely.

With the federal courts not only available but experienced in trying terrorism cases, permitting transfers for trial seems like the obvious choice.

Before Congress banned transfers to the U.S. for trial, one former Guantanamo detainee, Ahmed Ghailani, was transferred for trial in civilian court. Ghailani — who was held in a secret overseas detention facility by the CIA before being sent to Guantanamo in 2006 — was tried and convicted in federal court in New York for his role in the 1998 bombings of the U.S. embassies in Kenya and Tanzania. Ghailani, like so many accused of terrorism before and after him, is now serving a life sentence in the supermax prison in Colorado.

It is high time to abandon the flawed military-commission system, and the opportunity now exists to do so. When Congress resumes later this month, Montana senators should adopt new provisions in the NDAA that allow Guantanamo detainees to be transferred to the U.S. to stand trial in time-tested federal courts.

If the goal is truly to bring terrorists to justice and provide solace to their victims, then why try suspects in a system like Guantanamo’s that takes an inexcusable number of years to prosecute cases and magnifies the risks of being overturn on appeal?

The upcoming vote is a chance for lawmakers to show that they are truly committed to bringing terrorist suspects to justice.

W. Paul Smith is the counterterrorism associate at Human Rights Watch.