President Trump is airing his dissatisfaction with federal courts and certain justices he appointed to the Supreme Court, writing in a lengthy social media post that the legal system is stacked against him and his MAGA allies.

Mr. Trump took particular aim at U.S. District Chief Judge James Boasberg and the conservative-wing Supreme Court justices who ruled against his tariff policy in February.

“The Democrats on the Court always ‘stick together,’ no matter how strong a case is put before them — There is rarely even a minor ‘waver,’” Mr. Trump wrote late Sunday in a Truth Social rant that took multiple posts.

“But Republicans do not do this,” he posted. “They openly disrespect the Presidents who nominate them to the highest position in the Land, a Justice of the United States Supreme Court, and go out of their way, with bad and wrongful rulings and intentions, to prove how ’honest,’ ’independent,’ and ’legitimate’ they are.

The post underscored Mr. Trump’s lingering disgust with the Supreme Court for striking down his use of the International Emergency Economic Powers Act to impose tariffs on other nations.

The decision forced him to reconstruct his duties on imports — a central plank of his economic agenda — through more cumbersome authorities.

“The decision that mattered most to me was TARIFFS!” Mr. Trump posted. “The Court knew where I stood, how badly I wanted this Victory for our Country, and instead decided to, potentially, give away Trillions of Dollars to Countries and Companies who have been taking advantage of the United States for decades.”

Mr. Trump thanked members of the conservative wing who sided with him but decried the overall court as “little more than a weaponized and unjust Political Organization.”

His winding post attacked the judicial system for blocking his attempt to change the outcome of the 2020 presidential election, which he lost to President Joseph R. Biden.

But a recent decision by Judge Boasberg seemed to trigger his ire.

Judge Boasberg on Friday quashed the Department of Justice’s criminal probe into Federal Reserve Chair Jerome Powell, saying subpoenas about a Fed building renovation were a pretext to harass the central banker over interest rates.

Mr. Trump railed against the judge as biased against him and repeated his belief that there must be something fishy about cost overruns at the Fed project.