A federal judge questioned Texas's recently enacted law banning abortions after six weeks of pregnancy as the state clashed with the federal government in court Friday over the Justice Department's effort to block the measure.

U.S. District Court Judge Robert Pitman gave few signs during a Friday hearing about how he might rule, but at one point questioned the Texas legislature's novel approach of relying on private enforcement of the ban, which the Justice Department has called a "scheme to nullify the Constitution of the United States."

"I guess my obvious question to you is if the state is so confident in the constitutionality of the limitations on women's access to abortion, then why did you go to such great lengths to create this very unusual private cause of action rather than just simply doing it directly?" said Pitman, who was appointed by former President Obama.

Because of the way the bill was designed, state officials do not enforce the ban on abortions after six weeks; that role is left to private parties who bring civil suits in state court. 

The law, which went into effect a month ago, allows people to sue not just abortion providers but also anyone who aids people in getting an abortion. That could include those who transport patients to prohibited procedures. Successful plaintiffs can be awarded at least $10,000 in cases against illegal abortions, a regime that critics have likened to bounties for impeding a constitutional right to an abortion. 

That regime of private enforcement has thrown up procedural obstacles to the administration's legal challenge.

Brian Netter, the deputy assistant attorney general leading the DOJ's Federal Programs Bench, argued on Friday that the law's design was a naked attempt at skirting judicial review and called it an "open threat to the rule of law."

"Texas has made clear it does not want to follow the Supreme Court's precedents on abortion," Netter said. 

Texas is arguing that the Justice Department cannot bring the lawsuit in part because there are no state entities who could be subject to a court order blocking the ban.

"There is no public official who enforces the Texas Heartbeat Act," Will Thompson, a lawyer with the Texas attorney general's office, said during the hearing.

Thompson argued that the administration was resorting to "hyperbole and inflammatory rhetoric" to try and cast doubt on the legitimacy of the law.

The Justice Department argues that a federal judge could block the state court system from enforcing the law, known as S.B. 8. 

"If you look at each individual component of SB 8, they are all a piece of the puzzle, and the puzzle is designed unambiguously to create an array, to create a system and a picture where women trying to obtain an abortion – prior to viability, after six weeks, something that is clearly protected under the Supreme Court's binding precedents – they simply can't accomplish that goal because of the state action that erected those barriers," Netter said.

The state law is facing several legal challenges. Abortion providers had tried to get the ban blocked before it went into effect in a case that went before the Supreme Court.

In a 5-4 decision on the day the state law went into effect, the high court declined to block it, with Chief Justice John Roberts joining the three liberal members of the bench in dissenting against the five conservatives in the majority.

That order has embroiled the Supreme Court in political controversy in the weeks leading up to a new term that is loaded with consequential cases.

Updated at 1:25 p.m.