I've used 'fired' in the headline, but more accurately de Adder had his contract terminated with the Brunswick News, a privately-held publishing company that operates in New Brunswick, Canada. The sole owner, James K. Irving is one of the wealthiest people in Canada and he and his family have a vast array of interests and holdings, many of them dependent on access to the United States. So, when their little newspapers published a political cartoon that went viral completely excoriating the vile and hateful border practices of Trump something had to give.
Source: Daily Cartoonist
Michael de Adder was born, raised, and educated in New Brunswick province and was a regular presence in its newspapers. Brunswick News Inc., which owns the Saint John Telegraph-Journal, the Moncton Times & Transcript, and the Moncton Daily Gleaner, has now disassociated itself from de Adder.
The above cartoon is apparently the one that went a step too far for Brunswick News Inc.
According to Wikipedia de Adder “draws approximately 10 cartoons weekly and, at over a million readers per day, he is considered the most read cartoonist in Canada.”
Also, according to Wikipedia, de Adder is a past president of the Association of Canadian Editorial Cartoonists. In 2013, he was nominated for the National Cartoonists Society's Reuben Award for the top editorial cartoon in North America for a cartoon that depicted the NRA holding the Statue of Liberty with a gun to her head.
UPDATE: And this one--