The legislation dealt a blow to Hong Kong’s opposition forces on Tuesday even before it went into effect. Several prominent young activists bowed out of politics, a few groups disbanded, and some businesses distanced themselves from the pro-democracy movement. Opposition politicians quickly criticized the law for its power to silence dissent.

“It’s meant to suppress and oppress, and to frighten and intimidate Hong Kongers,” Claudia Mo, a pro-democracy lawmaker, said. “And they just might succeed in that.”…

“Those who have stirred up trouble and broken this type of law in the past will hopefully watch themselves in the future,” Mr. Tam said in a television interview. “If they continue to defy the law, they will bear the consequences.”…

Breaking from normal procedure, the committee did not release a draft of the law for public comment. Hong Kong’s activists, legal scholars and officials were left to debate or defend the bill based on details released by China’s state news media earlier this month.