Gov. Paul LePage has joined officials from 21 states – all but one controlled by Republican governors – to challenge in federal court a new U.S. Department of Labor rule that extends mandatory overtime to an estimated 4 million employees.

LePage was named as an individual plaintiff, and did not represent the state as governor, in the lawsuit filed Tuesday in Texas.

“If implemented, this rule would more than double the minimum salary threshold for public and private workers without congressional authorization,” LePage said in a statement. “The rule will force many state and local governments to substantially increase their employment costs. Some may be forced to eliminate some services and even lay off employees.”

President Obama initiated a rule change in 2014 that would rewrite the Fair Labor Standards Act’s overtime exemption for “white collar” employees. The final rule, approved in May by the Labor Department, would make any salaried employee making less than $47,500 a year eligible for overtime, to be paid at time-and-a-half. That’s double the current threshold of $23,660. The new overtime rule contains a provision to automatically increase the threshold every three years without going through the standard rule-making process.

Tuesday’s legal challenge seeks to halt the new rule from going into effect on Dec. 1. Critics have expressed concerns that the mandate might force employers to convert salaried workers to hourly workers or perhaps create more part-time jobs.

“Once again, President Obama is trying to unilaterally rewrite the law,” Texas Attorney General Ken Paxton said in a statement. “And this time, it may lead to disastrous consequences for our economy.”

The change would affect an estimated 16,000 workers in Maine, according to the U.S. Department of Labor. That’s about 3 percent of the state’s workforce, and represents only the second increase in the overtime salary ceiling since the 1970s. But employers expressed concerns this summer about the logistics of shifting employees from salary to hourly pay in order to calculate overtime.

LePage, in his statement, took a shot at Democrats for contributing to an unstable job market.

“This rule, coupled with referendum questions to dramatically increase the minimum wage and impose a 10.15% income tax on successful Mainers, demonstrates the Democrats at the state and national level are doing everything they can to put people out of work,” the governor said.

LePage’s communications director, Peter Steele, said his office had no additional comments about the lawsuit. In July, the Maine Department of Labor said it was working with employers to mitigate the potential impact.

LePage has not been shy about signing onto federal lawsuits against the Obama administration, many of which originate in Texas, a state whose attorney general has been aggressive in challenging the president and whose judges are solidly conservative.

In May, he joined several Republican governors in challenging the president’s directive that public schools should let transgender students use bathrooms or locker rooms that match their gender identity. As with the current lawsuit, LePage joined that court case in his personal capacity, not as a representative of the state.

In August, a federal judge blocked the Obama administration directive, but the ruling had little impact on Maine because of a 2014 Maine Supreme Judicial Court case that found schools cannot discriminate against transgender students.

In 2014, LePage joined several states in challenging the president’s executive actions on immigration, specifically his plan to protect from deportation more than 4 million parents of U.S. citizens and legal residents who have lived in the U.S. for at least five years.

And back in 2011, LePage’s then attorney general, William Schneider, joined a group of Republican-led states in challenging the Affordable Care Act.