Strikes against high-value terrorist targets require "near certainty" that the individual is who officials think and that civilians will not be killed as collateral damage, according to a newly declassified document that lays out how strikes are approved.

The document, which was posted online late on Friday, governs how the U.S. can nominate and approve drone and traditional strikes against terrorists outside the United States. It lays out the restrictive rules of engagement that have drawn some criticism from Capitol Hill in the fight against the Islamic State.

"Absent extraordinary circumstances, direct action will be taken only if there is near certainty that the action can be taken without injuring or killing non-combatants," the 18-page top-secret document says.

It also states that while many proposals are presented to the president for approval, some can be signed off on by the head of the agency that suggested the target. The president must sign off on a specific lethal strike against a high-value target only if the targeted individual is a U.S. citizen or if agency heads don't agree on the strike.

The document also speaks to how the U.S. should designate terrorists for capture, but states in no uncertain terms that the population of the detention center at Guantanamo Bay will not increase.

"In no event will additional detainees be brought to the detention facilities at the Guantanamo Bay Naval Base," it says.

Other rules governing when a lethal strike can be called include ensuring that capture was not possible, that the target posed a direct threat to the U.S., and that all laws were followed.

The document also allows for the president to make exceptions for the rules in cases where the U.S. is facing an imminent threat.

"Where there is a fleeting opportunity, the principal of one of the operating agencies may propose to the president that action be taken that would otherwise vary from the guidance contained in this [presidential policy guidance,] after a separate legal review has been undertaken to determine whether action may be taken in accordance with applicable law," it says.