Executions by lethal injection have been on hold for months
The US Supreme Court has rejected a challenge to the use of lethal injections to execute prisoners.
The court rejected by 7-2 the case made by two death row inmates in the state of Kentucky.
They sued the state in 2004, saying the commonly used combination of three chemical injections violated the US constitution's ban on cruel punishment.
Executions nationwide have been on hold since September. Virginia immediately said it was lifting its moratorium.
In a separate case, the Supreme Court is considering whether the death penalty can be applied for child rape.
During an execution by lethal injection, the inmate is given three drugs - a sedative, another that paralyses all muscles except the heart and a final drug which stops the heart, causing death.
States began using the three-drug method in 1978 as an alternative to historic methods of execution such as electrocution.
However, in recent years there have been botched lethal injection executions in Florida and California, in which inmates took up to 30 minutes to die.
A 2005 study also sparked controversy by suggesting the amount of sedation given might not be enough to stop the inmate feeling the painful effects of the other drugs - but would prevent him crying out.
Sodium pentothal - anaesthetic
Pancuronium bromide - paralyses entire muscle system
Potassium chloride - stops the heart
Chief Justice John Roberts said the petitioners had "not carried their burden of showing that the risk of pain from maladministration of a concededly humane lethal injection protocol, and the failure to adopt untried and untested alternatives, constitute cruel and unusual punishment".
Justices Ruth Bader Ginsburg and David Souter dissented.
Justice John Paul Stevens, although agreeing with the outcome, said the ruling would not bring an end to the lethal injection debate.
"I am now convinced that this case will generate debate not only about the constitutionality of the three-drug protocol... but also about the justification for the death penalty itself."
A total of 42 people were executed last year before the suspension. About 3,300 remain on death row nationwide.
A spokesman for Timothy Kaine, governor of Virginia, said the state would now proceed with executions as planned.
The Supreme Court was ruling on the case of two Kentucky death row inmates - Ralph Baze and Thomas Clyde Bowling Jr.
In 2004, Baze and Bowling - who had both been convicted of murder and sentenced to death - argued that lethal injections administered in Kentucky amounted to cruel and unusual punishment, violating the Eighth Amendment of the US Constitution.
That amendment is also being cited in a separate case in which the Supreme Court heard arguments on Wednesday, over whether the death penalty should be applied to a man found guilty of raping a child.
Patrick Kennedy was sentenced to death under Louisiana law for raping his 8-year-old stepdaughter.
His lawyer, Jeffrey L Fisher, argues that it would be a cruel and unusual punishment to execute his client for rape, since the death penalty is usually reserved for murder.
Five states, including Louisiana, permit executions for child rape.