(CNN) President Donald Trump's plans to reinstate a ban on transgender people serving in the military takes the US off a short list of countries that allow individuals to serve in the armed forces regardless of gender identity.

Trump's Twitter announcement on Wednesday reverses a year-old policy initially approved by the Defense Department under President Barack Obama, which was still under final review.

In June 2016, the Obama administration lifted a ban against transgender people serving openly in the armed forces. In 2011, Obama signed a repeal of the Clinton era "don't ask, don't tell" policy that blocked openly gay, lesbian, or bisexual individuals from joining the military but prohibited military personnel from harassing or targeting closeted LGBT members.

Without the US, 19 countries allow transgender people to serve. This includes Thailand, whose armed forces only allow transgender individuals to serve in administrative and office roles, not in combat.

In 1974, the Netherlands became the first country to grant transgender people the right to serve in the armed forces. Since then, a small list of countries have allowed their citizens to serve without any restrictions on sexual orientation or preferred gender.

Read More