An international volunteer organization urged Canadian authorities to arrest former U.S. Vice President Dick Cheney on war crimes charges when he visits the 2013 Toronto Global Forum later this week.

Lawyers Against the War argued in a letter dated Sunday that Toronto Police Chief William Blair and Ontario Attorney General John Gerretsen have a duty to arrest Cheney "as a person suspected on reasonable grounds of authorizing, counseling, aiding, abetting and failing to prevent torture.”

“Once Richard (Dick) Cheney enters Canada … Canada must ensure that Dick Cheney is either investigated and prosecuted for the indictable offence of torture in Canada or extradited to another country willing and able to do so," Lawyers Against the War's Gail Davidson wrote.

The letter contended that Toronto police are legally obligated to arrest Cheney to prevent him from “escaping to the United States.” The organization argued that Canadian law would legally allow authorities to do so:

Torture is also a crime under the Crimes against Humanity and War Crimes Act. Once Dick Cheney enters Canada, the torture (both the torture he has admitted to authorizing and the torture that he is accused of) are deemed to have been committed in Canada ...

Cheney has said he was "a big supporter" of waterboarding and other so-called enhanced interrogation techniques against terrorism suspects during his vice presidency. He and former President George W. Bush, along with other top Bush administration officials, were convicted in absentia of war crimes last year in Kuala Lumpur, Malaysia, for torture and cruelty. The verdict was largely symbolic.

Col. Lawrence Wilkerson, who served as chief of staff to former Secretary of State Colin Powell, also has accused Cheney of war crimes.

"Waterboarding is a war crime, unwarranted surveillance ... all of which are crimes. I don't care whether the president authorized him to do it or not, they are crimes," Wilkerson said in 2011.

Protesters of Cheney's September 2011 visit to Vancouver kept him locked inside the exclusive Vancouver Club -- where he had been scheduled to speak -- for seven hours before police could evacuate him safely.

Cheney canceled a trip to Toronto in March 2012, citing personal safety concerns.

Read the full Lawyers Against the War letter here.

Also on HuffPost:

Loading Slideshow...
  • Dick Cheney, Liz Cheney

    FILE - This Feb. 18, 2010 file photo shows Former Vice President Dick Cheney hugs his daughter, Liz Cheney, at the Conservative Political Action Conference (CPAC) in Washington.(AP Photo/Cliff Owen, File)

  • Dick Cheney, Liz Cheney

    Former Vice President Dick Cheney, accompanied by his daughter Liz Cheney, addresses the third annual Washington Ideas Forum at the Newseum in Washington, Thursday Oct. 6, 2011. (AP Photo/Manuel Balce Ceneta)

  • Dick Cheney, Liz Cheney

    Former U.S. Vice President Dick Cheney (L) speaks with his daughter Liz during the 2011 Washington Ideas Forum at the Newseum in Washington, DC, October 6, 2011. (JIM WATSON/AFP/Getty Images)

  • Liz Cheney, Dick Cheney

    Four-year-old Joshua McBride shows his Batman shirt to Liz Cheney and her father former Vice President Dick Cheney during a tour for their book, “In My Time-a Personal and Political Memoir”, at the Ronald Reagan Presidential Library and Museum on Tuesday Sept. 20, 2011 in Simi Valley, California. The books covers 40 years of the former vice president’s career in Washington. (AP Photo/David McNew)

  • Dick Cheney, Liz Cheney

    U.S. Vice President-elect Dick Cheney (L) is sworn into office by U.S. Supreme Court Justice Willaim Rehnquist (R) as his daughter Elizabeth (2nd R) holds the Bible, wife Lynne (3rd R) and daughter Mary (hidden) watch on Jan. 20, 2001 on the South Front of the U.S. Capitol. Bush was sworn in as the 43rd President of the United States. (TIMOTHY A. CLARY/AFP/Getty Images)

  • Dick Cheney, Liz Cheney

    Lynne Cheney (L), Vice President Dick Cheney and daughter Elizabeth 'Liz' sit in the Vice President office in the U.S. Capitol prior to President George W. Bush's State of the Union address January 29, 2002 in Washington, D.C. (Photo by David Hume Kennerly/Getty Images)

  • Liz Cheney, Dick Cheney

    Former Vice President Dick Cheney and daughter, Liz, held a lecture at the Richard Nixon Library in Yorba Linda., Calif., on Wednesday night Sept. 7, 2011. (AP Photo/Rose Palmisano/Orange County Register)

  • Liz Cheney, Dick Cheney

    Liz Cheney, board member, Keep America Safe, walks off the stage with her father, former Vice President Dick Cheney, after they addressed the Conservative Political Action Conference (CPAC), in Washington, Thursday, Feb. 18, 2010. (AP Photo/Cliff Owen)

  • Liz Cheney, Dick Cheney

    Former Vice President Dick Cheney responds to questions posed by his daughter Liz Cheney during a talk on his book, “In My Time-a Personal and Political Memoir”, which was co-authored by his daughter Liz Cheney, at the Ronald Reagan Presidential Library and Museum on Tuesday Sept. 20, 2011 in Simi Valley, California. (AP Photo/David McNew)