The American Institute for International Steel (AIIS) filed a lawsuit challenging President Trump’s tariffs on imported steel and aluminum, The Hill reports.

The trade association and two member companies claim Trump’s 25% tariffs on steel and 10% on aluminum are unconstitutional because they represent an improper “delegation of legislative power to the president,” and violate the doctrine of separation of powers, according to The Hill.

“According to the complaint, AIIS is concerned that the tariff increase will negatively affect its member companies by forcing them to raise prices, which would result in losing business and having to lay off workers,” writes Avery Anapol of The Hill.

The suit, filed in the U.S. Court of International Trade, asks the court to block the Trump administration from enforcing the tariffs.

The Section 232 tariffs were applied to steel and aluminum on the grounds of national security. Announced in March, the tariffs were eventually applied to U.S. allies, including Canada, Mexico, and the EU, on June 1 after an initial month-long exemption.

While domestic steel and aluminum producers have benefited from the tariffs, steel using companies are struggling under the weight of the duties.

In early June, Missouri-based Mid Continent Nail Corp. announced it was laying off 60 workers after losing 50% of its business in the first two weeks of June, according to Missourinet.

The continued tariff on steel wire from Mexico could prompt the nail manufacturer to cut 200 more jobs by the end of July, Missourinet reports.

Mid Continent, which uses the Magnum Fastener brand name, traces its history to 1952 when Don Cesar M. Gutierrez started a small wire shop in Mexico supplying handmade chain link fence using second hand wire purchased from the U.S. Mid Continent has been in Missouri for 25 years and a subsidiary of Mexico-based Deacero since 2012.

“The manufacturer’s existence in Missouri is riding on whether the federal government will grant a tariff (exclusion) on the steel wire it gets from Mexico,” Missourinet reports.

But the Commerce Department is struggling to handle a backlog of exclusion requests. So far, more than 22,500 exclusion requests from 300 companies have been filed, though less than half have been made available for public comment. Lag time between filing and being published on regulations.gov typically lasts about three weeks. Once public, domestic steel manufacturers have 30 days to file an objection, after which Commerce has 90 days to make a decision on each exclusion.

The 232 tariffs have been condemned by Senate Republicans who expressed concerns about costs passed on to manufacturers and consumers by higher-priced metals.

“These tariffs do not support U.S. national security,” Finance Committee Chairman Sen. Orrin Hatch, R-Utah, said. “Instead, they harm American manufacturers, damage our economy, hurt American consumers and disrupt our relationship with long-term allies while giving China a free pass.”

The Trump administration has collected more than $775 million from the metals tariffs since they were imposed in March, Bloomberg reports. The total is expected to exceed $1 billion with the next six weeks.