Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a reporter at Newsday since 1997.

For generations, states’ rights served as a rallying cry for conservative causes.

Now progressives are invoking them against President Donald Trump.

Deep-blue California, the largest state by population, which Hillary Clinton carried by 4 million votes, has retained former U.S. Attorney General Eric Holder just to help sue the federal government.

One sign of the role reversal appeared this week when 16 Democratic state attorneys general signed a friend-of-the-court brief against the Republican president’s executive order curbing immigration from seven nations.

New York’s Eric T. Schneiderman was among the signers, supporting a Washington state federal court suit opposing the 90-day Trump ban.

For years, Democrats pushed immigration law reforms as a federal issue. Blue-state officials, however, now argue that the travel ban harms state residents, employers, and educational and medical institutions.

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The Trump administration cites its broad legal powers over immigration, which President Barack Obama invoked in his own executive orders. The White House says the states have no standing.

Whatever the outcome, other states’ rights disputes are likely to arise.

Late in the Obama years, Republican-run Texas, Louisiana and Kansas were among the states fighting the Affordable Care Act — for example, trying to abolish a fee states had to pay to cover costs. They called this an “unconstitutional tax.” Before that, 27 states tried but failed to abolish the Obamacare outright.

Now, states bent on challenging Trump and allies over Obamacare’s repeal may focus on whatever comes along to replace it.

They also may take aim at GOP plans to pay for Medicaid through block grants to the states.

If the U.S. Supreme Court reverses Roe v. Wade — which in 1973 voided a state law banning abortions except to save the life of the mother — both red and blue states presumably would regain control of the issue.

We have seen some of this in recent years.

In New York during the George W. Bush administration, Eliot Spitzer as attorney general saw himself as filling a regulatory void when he used state statutes to crack down on Wall Street abuses.

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And with Trump & Co. moving to peel back all manner of regulations on the federal level, watch for states to assert their sovereignty in fields such as energy and the environment.

The 10th Amendment to the U.S. Constitution says: “The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.”

How to interpret that in 2017 could frame the skirmishes to come.