It also punishes what it calls “preparatory acts” of these crimes, and the theft of state secrets.
Rights watchdogs have criticized the ambiguous, catch-all language of the law.
Democrat legislators have said the law in Macau is intended by China to set an example for less pliant Hong Kong.
The Chinese government says the law is to fulfill Article 23 of the Basic Law governing the return of the former Portuguese colony of Macau and former British colony of Hong Kong to Chinese sovereignty.
It provides for sentences of up to 30 years for political crimes.
Its passage in Macau met with broad public acceptance in the territory, a Special Administrative Region (SAR) of China.
In neighboring Hong Kong, earlier Chinese government efforts to pass the law prompted huge protests in 2003.
Democratic legislators in Macau and Hong Kong agree the significance of the law’s easy passage in Macau lies in the example it sets for Hong Kong.
When the bill was passed last week Macau’s Secretary for Administration and Justice, Florinda da Rosa Silva Chan, said the authorities would work to strike a balance between protecting national security and safeguarding residents’ rights.
But critics are not convinced.
“The state security law will never be a good law because it can be used to repress political enemies,” said Macau legislator Antonio Ng Kuok-cheong, one of two members of Macau’s 29-member Legislative Assembly to vote against the bill last week.
“There are some Grey areas where the police could abuse their authority,” he told the BBC, as the law came into effect.
Mr Ng said there was no code to define what are “preparatory acts” of treason, secession or subversion, and while such cases might not result in prosecutions, the loose wording could be used to detain and harass political opponents.
He said Macau’s local government already had more than enough means at its disposal to control society.
“So why do we need this law in Macau? The intention of China is to make Macau an example to Hong Kong,” he said.
Hong Kong fears
“I agree the law in Macau is to set an example for Hong Kong – but it’s not a good example,” said Law Yuk-kai, director of the Hong Kong Human Rights Monitor.
He pinpointed the low threshold for political activity, freedom of speech and assembly in the security law.
“Lots of activities could be caught up in that, from demonstrations to simply making any political demand,” he noted, adding the law offered ambiguous wording and few safeguards.
Civic Party lawmaker Margaret Ng Ngoi-yee said it was a sad day for Hong Kong. “Inevitably, there will be greater pressure to revive Article 23 in Hong Kong,” she said.
Macau’s immigration authorities have recently outraged Hong Kong sensibilities by refusing entry to a photographer from a local newspaper, as well as to several pro-democracy politicians.
By Vaudine England, BBC News, Hong Kong, 3 March 2009