Repeal of a 1993 law that allowed gays to serve only so long as they kept their sexual orientation private took effect Tuesday at 12:01 a.m. EDT.
The dropping of “don’t ask, don’t tell” means service members can now reveal they are gay without fear of investigation or discharge. Some in Congress still oppose the change, but top Pentagon leaders have certified that it will not undermine the military’s ability to recruit or to fight wars.
“Repeal Day” parties have been organised across the country to mark the victory for gay rights.
The US Congress voted last year to repeal the law, which was introduced in 1993 under the Clinton administration.
It replaced an outright ban on gay people serving in the military.
Under the policy, gay people were permitted to serve as long as they did not openly acknowledge their sexual orientation, while commanders were not allowed to ask.
Pentagon press secretary George Little told reporters on Monday that the Department of Defense was fully prepared for repeal, and that 97% of military personnel had received training on the new law.
The armed forces have been accepting applications from openly gay recruits for a number of weeks and will begin processing them now that the new law has taken effect.
The military has also published a revised set of regulations, without references to any ban against homosexual service members.