David Haigh of UAE legal advisory firm Stirling Haigh called for clearer definition and application of the law - strict regulations and punishments exist despite the overt existence of gay and transgender communities and venues throughout the region.
The pair, who had arrived in the capital of the United Arab Emirates (UAE) on Aug 8, were arrested while out buying lunch at a shopping mall and were sentenced on Aug 20.
Fadli's elder brother Saiful Rahman told reporters earlier that his family only heard about the arrest through Fadli's friends five days after the fact.
Qistina is in the process of transitioning into a woman and had changed her name, but her gender is still stated as "male" on her passport.
A non-governmental organisation "Detained in Dubai" published an article regarding the background on the arrest and conviction of the duo on LinkedIn.
However, an Arabic court document said that the two Singaporeans were arrested for wearing women's clothes in public and for behaving indecently.
"The UAE has built a tolerant, cosmopolitan image, but the laws continue to reflect the conservative, traditional values of the society". A British man in the UAE faced charges of "cross dressing" past year, but Stirling said she helped him leave the country after paying a fine of 5,000 dirhams ($1,360).
"We have a family WhatsApp group and Fifi often sent us messages whenever she was away".
Fadli's family said they have not spoken to him since he sent them a selfie on Aug 9. This time, she suddenly went silent and this was out of character.
The pre-op transgender woman who was jailed visited the UAE many times in the past without incident, her friends say. A few days later, we received a voice message from her saying she had been arrested.
Singapore's Foreign Minister Vivian Balakrishnan told Muhammad Fadli's family the government was looking at ways to help the two men.
Reports said that Fadli and Nur have until Sep 4 to appeal against their sentence.
"I'm sorry to hear about this". I understand that they are already in contact with you and your brother. "Please let me know if you need further assistance", he said in a statement.