Trump has made these threats as part of his campaign rhetoric, vowing to prosecute or jail political rivals if elected.
The ACLU and other groups argue it violates the First Amendment and Supreme Court precedent on separation of church and state.
The summit aims to showcase Russia's continued international engagement and economic ties with developing nations.
Trump has attacked journalists for their coverage and has suggested they should face legal consequences for refusing to reveal sources.
Legal experts warn that just the threat of prosecution can deter individuals from opposing the president due to potential legal costs and stress.
Former Trump staffers and others are preparing for the worst, fearing he will act on his threats to punish perceived enemies.
Concerns are that the Supreme Court could overturn precedents on church-state separation, potentially weakening the First Amendment.
The summit is a PR coup for Russia, showing it is not isolated and highlighting its economic ties with developing nations.
They aim to create new financial mechanisms to sanction-proof their economies from Western influence.
An NPR investigation has found former President Donald Trump has made more than 100 threats to investigate, prosecute, jail or otherwise punish his perceived opponents - including private citizens. A federal court in Louisiana is weighing whether a state law requiring the Ten Commandments be displayed in public schools is constitutional. And Russian President Vladimir Putin is hosting a summit of world leaders despite the west trying to isolate him over the war in Ukraine. *Want more comprehensive analysis of the most important news of the day, plus a little fun? Subscribe to the Up First newsletter).Today's episode of Up First was edited by Barrie Hardimon, Susanna Capeluto, Ryland Barton, Lisa Thomson and Alice Woefle. It was produced by Paige Waterhouse, Nia Dumas and Kaity Kline. We get engineering support from Andie Huether. And our technical director is Stacey Abbott. *Learn more about sponsor message choices: podcastchoices.com/adchoices)NPR Privacy Policy)