California Attorney General Xavier Becerra, who President-elect Biden announced Monday will be his nominee for Health and Human Services secretary, has been one of the most litigious attorneys general against the president in recent years, actively pursuing progressive policies in the courts more than perhaps any other attorney general. 

Suits brought by California under Becerra have ranged from challenges to federal rules on religious exemptions to providing contraceptives for employees, rules on international students and online classes, the environment, immigration and more.

California has sued the Trump administration more than 100 times under Becerra. According to the Sacramento Bee, the price tag of those suits as of August was $43 million. 

"With the NEPA lawsuit, we have sued @realDonaldTrump 100 times," Becerra said in a tweet in late August. "And while we don’t go looking for a fight, we’re prepared to act when the people, resources, and values of California are at stake."

In this Thursday, Aug. 2, 2018, file photo, California Attorney General Xavier Becerra talks to reporters after a news conference at UCLA. President-elect Joe Biden has picked Becerra to be his health secretary, putting a defender of the Affordable Care Act in a leading role to oversee his administration’s coronavirus response. (AP Photo/Jae C. Hong, File)

In this Thursday, Aug. 2, 2018, file photo, California Attorney General Xavier Becerra talks to reporters after a news conference at UCLA. President-elect Joe Biden has picked Becerra to be his health secretary, putting a defender of the Affordable Care Act in a leading role to oversee his administration’s coronavirus response. (AP Photo/Jae C. Hong, File)

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In one of the more high-profile suits that California took the lead on under Becerra, the state sued HHS over a rule it issued that expanded the exemption for certain private organizations or companies to decline to provide contraceptives that the owners believe go against their faith. 

Becerra's office said in court that the rule was "illegal" and privileges "religious beliefs over secular beliefs as a basis for obtaining exemptions under the ACA."

"Defendants have violated the establishment clause because the new IRFs goes too far in accommodating an employer's religious objections to birth control, placing an undue burden on third parties – the women who seek birth control," the suit said. 

With the support of Becket Law – a nonprofit firm that aims to protect religious freedom – the Little Sisters of the Poor stepped in to argue against the California suit. It made it to the Supreme Court's doorstep before the court ruled in favor of the Little Sisters in a different case they were involved with in Pennsylvania. 

That case led the justices to also resolve the California case in favor of the Little Sisters, sending it back down to lower courts for further action consistent with the Pennsylvania case. 

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Perhaps the biggest case California has weighed in under Becerra is California v. Texas, the case on the constitutionality of the Affordable Care Act (ACA) that was argued in November and took center stage during the confirmation of Justice Amy Coney Barrett. 

The Trump administration declined to defend the ACA against a constitutional challenge by a coalition of red states. Filling that void, a coalition of blue states, led by California and Becerra, stepped in to support the law. California Solicitor General Michael J. Mongan argued in the Supreme Court in favor of the ACA last month.

The justices –  most notably Brett Kavanaugh –  seemed to be more receptive to the points from California and a lawyer representing the Democrat-controlled House of Representatives than they were to Texas Solicitor General Kyle Hawkins and Acting U.S. Solicitor General Jeffrey Wall arguing against the law. Most legal observers expect the court to uphold the ACA. 

"American lives and livelihoods are on the line, but we're confident that the law is on our side," Becerra said on the day of the oral arguments in the suit. 

California also secured a major win in a case in which it assailed, on administrative law grounds, Trump's effort to end Deferred Action on Childhood Arrivals (DACA). The 5-4 majority opinion, written by Chief Justice John Roberts, ruled the ending of DACA was "arbitrary and capricious." It also sparked a spirited dissent from Justice Clarence Thomas, who assailed his fellow justices for the "timidity" of the majority ruling.

Becerra has also been involved in multiple cases involving abortion, advancing pro-choice causes. This earned him praise from those on the left. Becerra in late 2019 was included on a list of potential Democratic Supreme Court picks by the progressive judicial group Demand Justice thanks to his reputation for active progressive litigation.

The same actions, meanwhile, have rankled conservative religious groups. 

"Far from ‘uniting’ the country, Biden has proven yet again he is an extremist on abortion," Susan B. Anthony List President Marjorie Dannenfelser said in a statement Sunday. "Becerra is aggressively pro-abortion and a foe of free speech. As attorney general of California, he continued what his predecessor Kamala Harris started by persecuting citizen journalists who exposed Planned Parenthood’s role in baby parts trafficking. Not only that, he went all the way to the Supreme Court to try to force California’s pro-life pregnancy centers to advertise and refer for abortion – a policy the court rejected as unconstitutional."

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The cases Dannenfelser was referencing were National Institute of Family and Life Advocates (NIFLA) v. Becerra and People of the State of California v. David Daleiden and Sandra Merritt.

In the NIFLA case, Becerra defended a California law requiring pro-life pregnancy centers to notify patients that California provides free or low-cost abortions. The Supreme Court eventually ruled 5-4 against the law on the grounds that it violated the First Amendment.

Daleiden and Merritt in 2015 recorded undercover videos of Planned Parenthood officials discussing fees for fetal body parts. There is still criminal and civil litigation ongoing in the matter. 

"As HHS secretary, [Becerra] will have extraordinary control over health care policy and particularly the levers of ObamaCare that were used to penalize religious groups, rights of conscience, abortion policy and real issues," Brian Burch, the president of the right-leaning Catholic Vote, told Fox News. "And this is of deep concern to people of faith and to the medical community across the country."

The naming of Becerra for HHS secretary has also drawn some early opposition from Republicans in Congress. Sen. Tom Cotton, R-Ark., said in a tweet that he will vote against Becerra's confirmation and that he "should be rejected by the Senate."

Added Sen, Mike Braun, R-Ind.: "I have serious concerns about Xavier Becerra’s ability to lead Health and Human Services because he has accepted over $1,000,000 in donations from the big healthcare industry and has a 100% rating from Planned Parenthood."

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"While Democrats boycotted the hearing for President Trump’s HHS nominee," Braun continued, "I will meet with Xavier Becerra to ask how his political donations from insurance companies and his support for abortions and 'Medicare-for-all' make him qualified to serve as the secretary of Health and Human Services."

The Biden transition, meanwhile, praised Becerra as "a longtime champion of expanding access to health care" and highlighted the fact that Becerra not only defended the ACA in the Supreme Court but while he was in Congress "helped drive passage of the Affordable Care Act."

In a tweet Monday, Becerra also promised to "build" on his work on the ACA at HHS. 

"In Congress, I helped pass the Affordable Care Act. As California's Attorney General, I defended it," he said. "As Secretary of Health and Human Services, I will build on our progress and ensure every American has access to quality, affordable health care – through this pandemic and beyond."

Fox News' Evie Fordham contributed to this report.