But, he says, that's not the judgment of the public servants who made the call.
NDP Leader Tom Mulcair is accusing the Conservative government of giving special treatment to Black by agreeing to let him return to Canada after he is released from an American prison this week.
Black has been granted a one-year temporary resident permit.
He is expected to be released from a Florida prison by Friday.
Harper says the decision to admit Black was taken by public servants, not politicians.
"There has been no involvement of anyone on the political side of government in this," Harper said in question period in the House of Commons.
"It would be just as easy for us if Mr. Black were not allowed to come to Canada, but that is not the judgment of those that administer the law."
Mulcair doesn't buy that.
"Thousands of people are following the rules and waiting their turn to be admitted to Canada," he said. "The Conservative government is giving a free pass to Conrad Black, a British criminal who is still jailed in an American penitentiary."
Mulcair said friends of the Tories get special consideration.
"Conrad Black is a British citizen, he is still in a U.S. jail, he was convicted of serious crimes in the United States. Why is he being given special treatment?
"No one else has ever been in that situation, of being still in jail having his dossier marched around all the offices of the minister and getting his approval before even getting out of the slammer."
Harper said Mulcair's claims are groundless and intemperate.
"If the leader of the NDP is suggesting the law should be changed, I would be delighted to see what those changes would be," the prime minister said.
"We on the government side have to administer and have to let our public service administer the law as it is and not apply political criteria to admissibility or non-admissibility."
The Montreal-born Black surrendered his Canadian citizenship in 2001 to accept a peerage in Britain's House of Lords.
His controversial business dealings while running Hollinger's global media empire ended with fraud and obstruction of justice convictions in 2007. He spent several years in a Florida prison.
Black has said he hopes to return to Toronto, where he and wife Barbara Amiel still own a home.
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