MANILA (UPDATE) — The contentious anti-terrorism law will take effect in 2 weeks, Malacañang confirmed Saturday, as critics who feared the legislation could be used to silence dissent prepared to challenge it before the Supreme Court.

The law that President Rodrigo Duterte signed on Friday would be imposed on July 18, 15 days after its publication on the state journal Official Gazette, Presidential Spokesman Harry Roque confirmed to ABS-CBN News.

Justice Secretary Menardo Guevarra, meanwhile, said Saturday afternoon that the law may take effect on July 19, 15 days after publication on the gazette on July 3, citing a rule where the first day is excluded and the last day is included.

The law, which was passed as the country grappled with the coronavirus pandemic, would let Duterte appoint a council that could order warrantless arrests of people it deems are terrorists.

It also allows for up to 24 days of detention without charge, which the government argues is necessary to combat long-running communist and Islamist insurgencies.

"The signing of the... law demonstrates our serious commitment to stamp out terrorism, which has long plagued the country and has caused unimaginable grief and horror to many of our people," Roque said Friday.

The law defines terrorism as intending to cause death or injury, damage government or private property or use of weapons of mass destruction to "spread a message of fear" or intimidate the government.

Critics allege the legislation also strips away old safeguards, such as penalties against law enforcers for wrongful detention of suspects.

• READ: The Anti-Terrorism Act of 2020

"By signing the anti-terrorism bill into law, President Duterte has pushed Philippines democracy into an abyss," said Phil Robertson, deputy Asia director for Human Rights Watch.

"The law threatens to significantly worsen the human rights situation in the Philippines, which has nosedived since the catastrophic 'war on drugs' began four years ago," Robertson added.

In a report last month, the UN human rights office said at least 8,663 people have been killed in the drug war with "near impunity" for offenders.

Several opposition lawmakers and groups have vowed to question the law before the Supreme Court.

• Opposition lawmakers say ready to question Anti-Terror Law before Supreme Court
• 'Draconian': Groups condemn anti-terror law signing, vow to challenge measure

Progressive group Bayan Muna last month said it was "researching" its next legal step if Duterte approved the law in which the definition of terrorism is allegedly vague and could strengthen the government's campaign against critics.

Retired Supreme Court Senior Associate Justice Antonio Carpio in June also urged the public to "all work to have the objectionable provisions in the Anti-Terrorism Act invalidated by the Supreme Court or repealed by Congress."

Government officials say alarm about the law is overblown, citing provisions that exempt "advocacy, protest, dissent, stoppage of work... not intended to cause death or serious physical harm."

— With a report from Agence France-Presse