The bill, which has been criticized by both the Japanese Bar Association and the United Nation's Special Rapporteur, was passed early Thursday by Prime Minister Shinzo Abe's ruling coalition, who hold a majority in the Diet, the nation's Parliament.
According to Abe, the new laws will help to crack down on terrorism and organized crime in Japan ahead of the 2020 Tokyo Olympics by allowing police to arrest individuals and groups planning to commit offenses.
"The law to punish terrorism preparation has just (been) enacted," he said Thursday. "We would like to implement the law appropriately and effectively in order to protect the lives and the assets of the Japanese people."
But the Japanese Bar Association said in a statement the law would "highly likely infringe civil liberties," adding under the legislation people protesting a building site could be imprisoned.
In a letter to the Japanese government on May 18, the UN's Special Rapporteur on the Right to Privacy, Joseph Cannataci, criticized the breadth of the legislation
, including the wide range of crimes which people can be arrested for planning.
"I am concerned by the risks of arbitrary application of this legislation given the vague definition of what would constitute the "planning" ... and given the inclusion of an overbroad range of crimes ... which are apparently unrelated to terrorism and organized crime," he said.
'Substantial expansion of police power'
Under the new laws, it will make it illegal to plan to commit 277 criminal actions, from arson to copyright infringement.
Koichi Nakano, political science professor at Tokyo's Sophia University, told CNN the new legislation "fundamentally" changed Japan's legal system.
"Unless a crime in committed in Japan, you don't get punished ... now if they think you are thinking of preparing to commit a crime, even before you're arrested, you'll be put under surveillance," he said.
"It leads to a substantial expansion of police power to investigate people and put them under surveillance."
Nakano compared the new legislation to the Peace Prevention Law enacted in Japan in 1925, which led to the country's infamous Thought Police.
"At that time, they reassured people that ordinary people won't be affected. But the law was abused, it persecuted communists, and then religious leaders, leaders and ordinary people," he said.
'Democracy in handcuffs'
Jeff Kingston, Asian Studies director at Japan's Temple University, told CNN Abe was using fear to crack down on Japanese society.
"The government has been trying to use extensive fear mongering as a way to justify curbing civil liberties and putting democracy in handcuffs," he said.
"They are giving the police extensive powers and criminalizing things that ought not to be a crime in a democracy."
The laws have provoked protests since December, growing in intensity over recent weeks, after the extent of Abe's new laws became public knowledge.
Opposition Democratic Party leader Renho said she felt "unspeakable anger" at the law's passage through the Diet.
"The enactment of the law allowed a breeding ground for problems in the lives of citizens. Prime Minister Abe and the coalition partners owe a very significant responsibility (for) it," she said in a statement.