The recent Hong Kong court's judgment imposed on a man who desecrated the Chinese national flag during an anti-government protest has failed to recognize the seriousness of the case, as the flag is a symbol of national sovereignty, dignity and the "one country, two systems" principle, legal experts said on Thursday.

They thought the man's sentence, a mere 200 hours of community service, would have no deterrent effect on society. The case was the city's first－one of several involving national flag desecration during recent protests－to receive a judgment.

The remarks came after the Sha Tin Magistrates' Courts in the Hong Kong Special Administrative Region on Tuesday sentenced 21-year-old technician Law Manchung to 200 hours of community service for one count of desecrating the national flag.

Law had pleaded guilty to trampling on a national flag and throwing it into a garbage bin, which he then tossed into a river in Sha Tin, New Territories, on Sept 22.

According to the National Flag and National Emblem Ordinance, a person who desecrates the national flag can face up to three years in prison.

Willy Fu Kin-chi, a law professor and member of the Chinese Association of Hong Kong and Macao Studies, stressed that the nature of the defendant's behavior was very serious, as he "deliberately challenged the national sovereignty", and undermined the "one country, two systems" principle.

The sentence of community service was "too lenient", Fu remarked. He said only a prison sentence can deter people from committing similar crimes.

Lawrence Ma Yan-kwok, a barrister and chairman of the Hong Kong Legal Exchange Foundation, agreed that the sentence was too light compared to previous cases in the SAR.

He referred to a case in August when a man was sentenced to four weeks in jail for spray-painting "China will win" on the gate of the United States Consulate General in Hong Kong to protest US interference in Hong Kong's internal affairs.

Ma said the court neglected the fact that a national flag is the symbol of national dignity.

He urged the Department of Justice to file an appeal against the judgment.

Ronny Tong Ka-wah, a barrister and member of the Executive Council, the chief executive's top political advisory body, pointed out that under the "one country, two systems" principle, desecrating the nation's symbol should not be punished more leniently than defacing the gate of a foreign consulate.

Previous judgments over these crimes varied largely from each other, Tong said, citing a case in 2013, where activist Koo Sze-yiu was sentenced to nine months in jail for burning a national flag.

He said he "absolutely agrees" that the court must establish clear sentencing guidelines for flag desecration.

In handing down the verdict, Magistrate Lee Chi-ho admitted the seriousness of Law's behavior, but said it was no more serious than burning a national flag.

After the court judgment on Tuesday, Hong Kong's former chief executive Leung Chun-ying said the lenient sentence will trigger public outrage in the whole country and urged the Department of Justice to lodge an appeal.