The US House of Representatives has passed a bill defining the rules for interrogating and trying foreign terrorism suspects.
Several hundred detainees are being held at Guantanamo Bay
The bill, backed by President George W Bush, would allow military tribunals to try the several hundred suspects held at Guantanamo Bay in Cuba.
Supporters say the bill gives America the tools it needs to bring terror suspects to justice.
Critics say it curbs the rights usually granted in civil and military courts.
The legislation is a response to a Supreme Court ruling in June that the original military tribunals set up by the Bush administration to prosecute detainees were in violation of American and international law.
The new measures provide defendants with more legal rights than they had under the old system, but it eliminates their right to challenge their detention and treatment in federal court.
The bill forbids treatment of detainees that would constitute war crimes - such as torture, rape and biological experiments - but gives the president the authority to decide which other techniques interrogators can use.
The Senate is expected to vote on a near-identical bill on Thursday, which if also passed, would give President Bush and Republicans a substantial victory before mid-term elections in November.
If the Senate bill is passed, military tribunals could resume under the new guidelines in early 2007.
There is the possibility however, that if this new legislation is passed, it could also be challenged in the Supreme Court.