The High Court on Wednesday heard a constitutional challenge against a law that criminalises sex acts between men.

At the end of the closed-door hearing, Justice Quentin Loh reserved judgment.

The case was brought by Mr Tan Eng Hong, 49, who had first filed a challenge against Section 377A of the Penal Code in 2010, after he was charged for having oral sex with another man in a a public toilet.

The Attorney-General's Chambers applied to strike out his bid but in August last year, the Court of Appeal allowed Mr Tan to have his day in court.

Mr Tan's lawyer, Mr M Ravi, argued that Section 377A was "inherently absurd, arbitrary, vague and discriminatory". As such, it does not have the required qualities to amount to a "law".

He argued that Section 377A violates the Constitution, which offers protection of equality before the law, as it provides for different treatment in similar circumstances.

But Senior Counsel Aedit Abdullah, for the AG's Chambers, argued that Section 377A is founded on an intelligible difference based on gender.

Last month, Justice Loh had also reserved judgment in a separate case on the constitutionality of Section 377A, filed by a gay couple, Gary Lim and Kenneth Chee in 2012.