The weekly published the photos online and in its print version, which hit the newsstands on Thursday.
After a five-week trial, Abdelkader Merah was last week sentenced to 20 years in prison and Malki to 14 for terrorist conspiracy for being implicated in his brother's killing spree.
Mohamed Merah died in a shootout with police after gunning down three soldiers, as well as a teacher and three children at a Jewish school in south-west France.
As in most countries, the taking of photographs is forbidden within French courtrooms while trials are in progress.
Paris Match could face a 4,500-euro fine, the confiscation of all copies of the relevant issue and an order to take the photos off its website.
Other reporters angered
The French legal correspondents' association condemned the magazine's "irresponsibility".
Lawyer Eric Morain complained that "after this we won't be able to complain that journalists can't use computers or tablets to live-tweet trials", claiming the paper had achieved "the lowest of the low in news in exchange for a future threat to newsgathering".
The paper's deputy head, Régis Le Sommier, was unrepentant on Thursday.
"It was a deliberate choice," he told the 20minutes freesheet, citing the "historic significance of the trial".
This is not the first time Paris Match has flouted the law on photographs.
In February 2008 it had its credentials withdrawn for publishing a photo of serial killer Michel Fournirel in court after he had refused to have his picture taken outside it.
In July a court banned it from republishing pictures of the 2016 Nice terror attack, judging them to be an "offence against human dignity".