In Ireland, a person can obtain a Gender Recognition Certificate and, later, a new passport to match their gender.Getty Images

Ireland's Department of Foreign Affairs (DFA) has this week updated its travel advice for Irish citizens, specifically transgender citizens, planning on traveling to the US.

Irish citizens traveling to the US must have a valid ESTA or US visa, the DFA's travel advice webpage for the US says.

"ESTA and visa application forms to the US require travellers to declare their sex," the DFA's updated US travel advice says.

"The US authorities have indicated that this should reflect the traveller’s biological sex at birth.

"Travellers who have an 'X' marker on their passport or whose sex on their passport differs from sex assigned at birth should contact the Embassy of the United States of America in Dublin for further details on specific entry requirements."

The DFA maintains its 'normal precautions' security status for the US.

Ireland joins Denmark, Finland, and the Netherlands in updating their US travel guidance this week regarding people's gender markers on their travel documents.

As of Thursday evening, the DFA had not responded to IrishCentral's request for comment on the matter.

While the ESTA and / or visa requirements for Irish citizens wishing to travel to the US aren't new, US President Donald Trump signed an executive order on his first day in office that declares there are only two sexes, which are "not changeable and are grounded in fundamental and incontrovertible reality."

In February, reporter Erin Reed obtained a memo issued by US Secretary of State Marco Rubio that provides guidance in light of the executive order.

The memo says in part: "... both immigrant and nonimmigrant visa applications request that an applicant identify their sex as either male or female.

"Moreover, all visas must reflect an applicant's sex at birth.

"To verify an applicant's sex, you should generally rely upon the documents provided by the applicant (including passport or birth certificate).

"If there is a discrepancy either in the applicant's documents or in electronic consular records, or if other evidence casts reasonable doubt on the applicant's sex, you should refuse the case under 221(g) and request additional evidence to demonstrate sex at birth.

"Typically, a timely-registered birth certificate with a sex marker will suffice for this purpose."

Meanwhile, the US Department of State "will no longer issue US passports or Consular Reports of Birth Abroad (CRBAs) with an X marker.

"We will only issue passports with an M or F sex marker that match the customer's biological sex at birth."

Gender recognition in Ireland

As per Ireland's Gender Recognition Act 2015, anyone over 18 can apply for a Gender Recognition Certificate in order to have their preferred gender recognized by the State.

An application can be made on behalf of a child aged 16 years or over if a court order is obtained that exempts the child from meeting the age requirement.

Once a Gender Recognition Certificate is issued, the gender of the person named on the certificate becomes, for all purposes, the preferred gender from that date forward. People with a Gender Recognition Certificate are able to apply for a new passport and apply to the General Register and get a new birth certificate.

The Irish Department of Social Protection's latest review of the Gender Recognition Act, published last June, found that since the Act came into effect in September 2015, 1523 of the 1582 applications received were granted. 21 of the applications granted were for people aged 16/17.

(The Department noted that applications received in one year may be granted in a subsequent year as applications await decision at the end of any given year.)

Since the commencement of the Act, 850 Irish passports have been issued to Gender Recognition Certificate holders, including 35 passports to holders aged under 18 years.

Also since the commencement of the Act, there have been 900 registrations on the Register of Gender Recognition. The vast majority - 654 - were aged between 18 and 30, while 17 were aged 16 - 17.