President Trump tweeted his decision to not endorse the commitment with fellow G7 nations, just hours after Canadian Prime Minister Justin Trudeau announced that all seven countries had signed the agreement, despite trade tensions.

The president went on to criticize Trudeau claiming that the prime minister "acted so meek and mild during [the G7] meetings." Trump blamed the reversal on a news conference the Canadian leader gave following Trump's departure saying, "US Tariffs were kind of insulting," calling the PM "Very dishonest & weak... Our Tariffs are in response to his of 270% on dairy!"

The intrigue: That last line could perk up ears at the World Trade Organization, as the White House had been saying that the U.S. tariffs are based on national security concerns. It was already a controversial justification, and Trump's tit-for-tat tweet creates new ammo for critics.

Go deeper: A new era of global trade wars