Some legal experts say the states' realignment could signal that the changes made last month to Trump's original executive order have strengthened the government's case.
Sixteen Democratic state attorneys general and the District of Colombia on Thursday filed a "friend of the court" brief backing Hawaii in its bid to block the March 6 executive order, which two federal judges put on hold before it could be implemented. Hawaii and other states argue the ban violates the U.S. Constitution because it discriminates against Muslims.
But Pennsylvania Attorney General Josh Shapiro, who opposed the original ban that Trump signed on Jan. 27, did not join Thursday's brief, which was filed in the 9th U.S. Circuit Court of Appeals in San Francisco. Shapiro declined to comment.
On the other side, Texas, which had been alone in its support for the original January order, has gained the support of 14 Republican states urging that the ban go forward in a legal brief filed on April 10. Those states back the government's argument that the president has wide authority to implement immigration policy and that the ban is needed to prevent terrorist attacks.
Trump's original ban, which the president said was needed for national security to head off attacks by Islamist militants, applied to seven Muslim-majority nations and indefinitely banned the entry of all refugees from Syria. It was revised and narrowed after a flurry of legal challenges.
"The second executive order was much more carefully written than the first. Maybe when various states analysed it they weren't as interested as joining," said Stephen Yale-Loehr an immigration expert at Cornell University Law School. However, he said, "amicus briefs sometimes are filed for political reasons."
Some judges pay close attention to amicus briefs, while others disregard them.
The U.S. Department of Justice declined to comment.
Trump's January order was hastily implemented just days after his inauguration, leading to chaos and protests at airports and more than two dozen lawsuits. A federal judge in Seattle halted the order and the 9th circuit upheld that ruling.
The changes were meant to chip away at the plaintiffs' "standing" to sue, which requires that anyone bringing a lawsuit show they have been directly harmed by the action they are contesting.
But as soon as the second order was signed, states and civil rights groups went back to court, saying that it was still discriminatory.
Federal district judges in Maryland and Hawaii put the second order on hold before it could take effect on March 16.
The judge in Hawaii blocked the two central sections of the ban, on travel and refugees, while the Maryland judge only halted the travel portion.
Most of the focus is now on the Hawaii case, which is being heard by the 9th Circuit on May 15.
The 4th Circuit appeals court in Virginia is slated to hear arguments in the Maryland case on May 8.
Not all states have staked out a side in the fight. Pennsylvania now is among 18 states, including Michigan, Ohio, and New Jersey that have not taken sides on the issue, opting not to file any legal briefs.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)