The phrase "act which was used" is correct and usable in written English.
It can be used when referring to a specific action or deed that has been previously mentioned or is known in the context.
Example: "The act which was used to justify the decision was controversial among the members."
Alternatives: "action that was taken" or "deed that was employed".
9am: Emergency debate on schedule 7 of the Terrorism Act, which was used to detain David Miranda, the partner of the Guardian journalist Glenn Greenwald, at Heathrow.
The Canadian federal government will probably review the transaction under its Investment Canada Act, which was used to thwart the BHP Billiton bid for Potash.
He described the Patriot Act, which was used by the NSA as authorisation for the bulk phone data collection, as a monstrosity.
It is June, 1917, when the Model Press Clipping Bureau closes its doors the same month that Woodrow Wilson signed the Espionage Act, which was used to lock up people like Eugene V. Debs, who by then had run for President four times as a socialist.
The Sedition Act, which is used to prosecute people who criticise the government and judiciary, was strengthened in 2015 to include jail terms of up to 20 years.
The release of the documents yesterday focused on section 215 of the Patriot Act, which is used to allow the bulk collection of US phone records.
The five were indicted under the Racketeer Influenced and Corrupt Organizations Act, which is used to fight organized crime and allows the government to seek stiffer penalties.
The BBC has long had powers to carry out targeted surveillance on those it thinks are dodging the licence fee under the Regulation of Investigatory Powers Act, which is used by other organisations including the police.
The PGS service falls under the FD&C Act, which is used to regulate products that are intended to diagnose, mitigate, treat or prevent disease or to affect the structure of function of the body.
Lewis interprets later historical events as affronts to freedom of speech, including the Sedition Act of 1918 which effectively outlawed criticism of the government's conduct of WW I; and the McCarran Internal Security Act and Smith Act, which were used to imprison American communists who where critical of the government during the McCarthy era.
The advice is implemented in the National Prevention of Disease Act, which is used by doctors in university and non-university hospitals to formulate guidelines on reduction of salt intake.
