WASHINGTON — Before ceding power, the Obama administration quietly removed a former extremist stronghold in Libya from a list of combat zones where United States counterterrorism drone strikes are authorized without obeying special rules intended to prevent civilian deaths, officials said on Friday.

The change means that as Donald J. Trump’s presidency begins, the United States is targeting Islamist militants in three known “areas of active hostilities,” where strict guidelines to protect civilians do not apply: Afghanistan, Iraq and Syria. For much of 2016, there was a fourth: The region around Surt, Libya.

It is not clear whether Mr. Trump will keep those civilian-protection rules — called the “Presidential Policy Guidance,” or P.P.G. — for airstrikes outside of active war zones. Issued by Mr. Obama in 2013, they require “near certainty” that a bombing will kill no civilians, and that the target must pose a threat to Americans — not just to American interests.

The Obama administration developed the guidelines in response to criticism that airstrikes were killing too many civilians, and in turn fueling anti-Americanism and helping terrorists recruit new members. But some military and C.I.A. officials have chafed under the limits.