ABC News' Ariane de Vogue reports: In a blow to the Obama administration, a federal judge in Florida today issued a ruling allowing parts of a lawsuit by 20 states challenging the recently passed health care legislation to proceed.

The two parts of the law that will proceed to trial are expansion of Medicaid and the individual mandate that requires qualifying individuals to obtain health insurance by 2014.

Of all the challenges to the health care law, this is one of the most interesting because of the numbers of states that have signed on. At issue today were mostly procedural issues not the core constitutional questions. The office of Judge Roger Vinson of the U.S. District Court for the Northern District of Florida who issued today's ruling, said the trial is scheduled to start in early December.

Attorney General Bill McCollum, who has spearheaded the effort against the federal government, released a statement saying: “This ruling is a victory for the states, small businesses and the American people. It is the first step to having the individual mandate declared unconstitutional and upholding state sovereignty in our federal system.”

In his ruling, Judge Roger Vinson explained: “I have not attempted to determine whether the line between Constitutional and extra constitutional government has been crossed. ... I am only saying... the plaintiffs have at least stated a plausible claim that the line has been crossed.”

Conservatives are praising the ruling. Carrie Severino, policy director and counsel for the Judicial Crisis Network released a statement saying: “Obama, Harry Reid, and company were hoping for something to brighten up their otherwise gloomy election season. But their hopes were dashed by Judge Vinson today because Obama's signature ‘achievement’ remains under a cloud of constitutional suspicion. In the fight between Obamacare and principled, limited government, round one goes to freedom.”

A federal Judge in Michigan, in a different case, recently ruled on the bigger question and upheld the constitutionality of the individual mandate.

ABC News' Huma Khan contributed to this report.

UPDATE: The White House said today that the ruling is "nothing new" and expressed confidence that its arguments will prevail.

"This is nothing new. We saw this with the Social Security Act, the Civil Rights Act, and the Voting Rights Act -- constitutional challenges were brought to all three of these monumental pieces of legislation, and all of those challenges failed. So too will the challenge to health reform," Stephanie Cutter, assistant to the president for special projects wrote in a blog post.

Cutter also warned against repealing the health care bill, saying it would have "devastating consequences for millions of Americans."