A federal judge on Monday voided the Biden administration's mask mandate for travelers using public transportation such as trains and airplanes.

The mandate from the Centers for Disease Control and Prevention applies to people as young as 2 years old, and had been set to expire a number of times but was recently extended to May 3 before Monday's ruling.

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The ruling from U.S. District Court Judge Kathryn Kimball Mizelle, came in a case brought in Florida federal court by Health Freedom Defense Fund, Inc. and frequent air travelers Ana Daza and Sarah Pope against the administration. Judge Mizelle determined that the mandate violated the Administrative Procedure Act by being outside the scope of the CDC's authority, was "arbitrary" and "capricious" and not going through the required notice and comment period for federal rulemaking.

Mizelle examined the section of the Public Health Services Act of 1944 that was the basis for the mandate.  That law allows the CDC "to make and enforce such regulations" deemed "necessary to prevent the introduction, transmission, or spread of communicable diseases from foreign countries into the States[.]" To achieve this, the law says that CDC can utilize "inspection, fumigation disinfection sanitation, pest extermination, destruction of animals or articles found to be so infect or contaminated as to be sources of dangerous infection to human beings, and other measures[.]" The administration, the judge noted, has claimed that the mask mandate falls under "sanitation."

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The judge noted that one could view "sanitation" as being an active measure to clean or as a preventative measure to keep something from getting dirty or infected, but through an examination of the statutory language, she determined it was the former. 

"The context of [the statute] indicates that ‘sanitation’ and ‘other measures’ refer to measures that clean something, not ones that keep something clean," Mizelle wrote. "Wearing a mask cleans nothing."

The judge also noted that the CDC's reasoning was flawed because the sanitation power only applies to property, not to people.

The ruling also poked a hole in the government's defense that the CDC's interpretation of the statute should be given deference in accordance with the landmark 1984 case of Chevron, U.S.A. v. Natural Resources Defense Council. Mizelle said Chevron only applies "'when the devices of judicial construction have been tried and found to yield no clear sense of congressional intent.'"

"A court may not rest on Chevron to avoid rigorous statutory analysis," Mizelle wrote, noting that the law in question "is not ambiguous."

Additionally, Mizelle ruled that the CDC improperly avoided the standard notice and comment process for rulemaking and that the exceptions the government invoked did not apply. The administration claimed both that the mandate was not a "rule" in the sense that required notice and comment, and that it qualified for the "good cause exception." The judge rejected both arguments, noting that the only reason the administration gave for good cause was the COVID-19 pandemic without giving specifics.

"The CDC's failure to explain its reasoning is particularly problematic here. At the time when the CDC issued the Mandate, the COVID-19 pandemic had been ongoing for almost a year and COVID-19 case numbers were decreasing," Mizelle wrote. "This timing undercuts the CDC's suggestion that its action was so urgent that a thirty-day comment period was contrary to the public interest."

Immediately following the announcement, United Airlines told employees that the mandate will remain in effect until they receive guidance from the federal government on how to proceed. 

Later Monday, an administration official told Fox News the agencies are reviewing the decision and assessing potential next steps. The official confirmed that the court decision means CDC's public transportation masking order is not in effect at this time. 

"Therefore, TSA will not enforce its Security Directives and Emergency Amendment requiring mask use on public transportation and transportation hubs at this time," the official said. "CDC recommends that people continue to wear masks in indoor public transportation settings." 

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Meanwhile, the Association of Airline Attendants said in a statement is "urging calm and patience among passengers" and that they're "hoping to avoid violence in the friendly skies while they gather legal analysis of what this ruling means for flights taking off right now." 

Fox News' Bradford Betz Bill Mears, Connie McDonough, Gillian Turner, and Pat Ward contributed to this report.