A federal judge in Massachusetts has stopped President Trump's plan to change US election rules. The judge supported a group of Democratic state attorneys general who argued that Trump's action was against the Constitution. Trump's executive order, issued in March, wanted to make people show proof of citizenship to register to vote. It also said that only mailed ballots received by Election Day would be counted, and that states would only get federal money for elections if they followed this new deadline. The White House said the order was to make sure elections were "free, fair, and honest." However, Judge Denise J. Casper decided that the states would probably win their legal cases. She stated that the Constitution does not give the President specific powers over elections. The ruling also blocked the part of the order that required states to reject any mail-in or absentee ballots received after Election Day. This is the second time a judge has ruled against Trump's election order, as a judge in Washington D.C. had already blocked parts of it.