In the motion filed Monday in the U.S. District Court of Eastern Oklahoma, the defense claims the state has no grounds to challenge the law.
>>Read the full text of the motion.
The attorneys for the federal government argue that Oklahoma is raising "hypothetical" concerns about the impact of the new law and that the state does not have "standing to litigate its citizen's rights and obligations under federal law."
Oklahoma Attorney General Scott Pruitt issued a statement Tuesday afternoon responding to the filing.
"Oklahoma's lawsuit has never been about the policy or politics of the Affordable Care Act; it is about the legality of the IRS rule and ensuring that the federal government complies with implementation of its own law," Pruitt said.
Oklahoma Attorney General Scott Pruitt filed the suit in January 2011 claiming that Congress had exceeded its authority by requiring minimum health insurance coverage for all Americans.
The district court stayed proceedings in the case until the Supreme Court ruled on a similar case.
The Supreme Court upheld the law this summer by stating the minimum coverage requirement was constitutional under Congress's taxing authority.
Oklahoma filed an amended complaint following the ruling. This week's motion from the federal government was a response to the state's amended suit.
The state has until December 31 to respond to the motion, according to the Attorney General's office.