Indonesia's President Joko Widodo has agreed to issue a regulation allowing the authorities to revoke the passports of citizens who support the Islamic State in Iraq and Syria (ISIS).

The move comes as more than 350 Indonesians are said to have joined the ISIS in the past two years. About one-third left Indonesia specifically to go to Syria, while the rest were already studying or working in the Middle East before they decided to fight alongside the militant group to set up a separate state.

However, there are worries that should the movement fail to achieve its goal, these radicalised Indonesians might return home and therefore pose a security threat to their own country.

"We will revoke the passports of those who plan to go abroad to join ISIS and those who are already abroad with ISIS. They cannot be allowed to come home," Coordinating Minister for Political, Security and Legal Affairs Tedjo Edhy Purdijatno told The Straits Times yesterday.

"We will come up with a regulation. It could be a presidential regulation," he added.

Mr Tedjo was speaking after he and Law Minister Yasonna Laoly as well as national police chief General Sutarman met Mr Joko yesterday afternoon to discuss new anti-terrorism measures.

"The government must first pass a regulation that clearly bans anyone from joining any organisation that promotes violence to achieve its goal. This rule must exist first, otherwise revoking the passports of ISIS supporters would have weak legal grounds," terrorism analyst Adhe Bhakti told The Straits Times. Indonesians who declare support for the ISIS cannot be arrested under the country's existing laws as long as they do not incite violence.

On Dec 27, six people planning to travel to Syria were arrested at the Soekarno-Hatta international airport. They were charged with using falsified documents to apply for their passport.

The meeting also discussed the need to improve deradicalisation measures and tighten security in prisons.

"Terrorist inmates must be more closely monitored in prison. They are now allowed to receive visitors. We will have to fix this," Mr Laoly added.

Agreeing, Mr Adhe said some inmates abused this right. He citied one instance where an inmate invited about 20 people and started to talk about militant ideology.

wahyudis@sph.com.sg