Labor unions took to social media and Capitol Hill Wednesday to demand that lawmakers end a free trade agreement which critics claim has hurt domestic workers.

Labor unions have long argued that domestic workers have been unfairly disadvantaged by the North American Free Trade Agreement (NAFTA). President Donald Trump has also been highly critical of the deal and is now looking to renegotiate it. The free-trade deal was first implemented in 1994 between Canada, Mexico, and the United States.

Trump and the labor movement don’t agree on much despite both being focused on helping workers. International trade is one of the few areas they have some common ground. Labor unions furthered their opposition campaign Wednesday by taking to social media and delivering 400,000 petitions to congressional lawmakers.

The Replace NAFTA campaign helped organize the demonstration against the trade agreement. The campaign is supported by Public Citizen, Citizen’s Trade Campaign, and the Sierra Club. The AFL-CIO, which is the largest federation of labor unions in the country, also supports the effort.

The Replace NAFTA campaign also hopes to eliminate what is known as the Investor-State Dispute Settlement (ISDS) system. The ISDS is a function of international law included in many trade agreements including NAFTA. It is a mechanism for using neutral arbitration to resolve investment disputes between companies and countries.

Trump broke with many others on the right by criticizing current trade policy during the campaign. He has already started the process of renegotiating NAFTA. The fourth round of negotiations started Wednesday with a meeting at the White House between the president and Canadian Prime Minister Justin Trudeau.

Labor unions used the opportunity to demand that the trade deal be replaced with something that helps workers. The AFL-CIO and the American Federation of Teachers (AFT) were among the unions that delivered 400,000 petitions to lawmakers. The unions have also launched informational campaigns and participated in protest against the trade agreement over the years.

The AFL-CIO has often argued that international trade agreements have been used to benefit large corporations at the expense of workers. NAFTA has become the main target for unions and many other critics. The AFL-CIO suggested earlier in the year that the trade deal be reformed to include new labor and procurement rules, consumer protections, and protections against currency misalignment and tax dodging.

Trump has made working-class issues a cornerstone of his administration. Immigration and international trade became major components of his agenda with concern cheap foreign labor is undercutting domestic workers. He has also expressed concern over currency manipulation by countries like China.

U.S. Trade Ambassador Robert Lighthizer detailed what the president hopes to accomplish June 22 during a congressional hearing. The administration plans to renegotiate trade deals to be fairer and more efficient, enforce trade deals more aggressively, and increase domestic exports.

Trump has already delivered on one major campaign promise by withdrawing from the Trans-Pacific Partnership (TPP). The agreement would have been the largest regional trade deal in history at roughly 39 percent of global GDP. Former President Barack Obama was unable to get much support from fellow Democrats when trying to get the deal implemented.

CNN reported that the trade negotiations might soon be facing challenges. President Trump, according to the reports, has made several proposals that threaten to undermine negotiations. Trump may then have an excuse to scrap the trade deal entirely and start from scratch.

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