President Donald Trump's most recent effort to curtail immigration from countries deemed unsafe by both his and the Barack Obama administration was dealt another judicial setback Thursday by a federal appeals court in Virginia.

In a 9-4 decision, the court ruled that President Trump's travel restriction is unconstitutional because it discriminates against Muslims, even though some of the countries in the list include North Korea and Venezuela. The majority ruling cited Trump's Twitter posts and other public statements as evidence that the stated intent behind the executive order - national security - is mere window dressing for its true intent.

"Examining official statements from President Trump and other executive branch officials, along with the Proclamation itself, we conclude that the Proclamation is unconstitutionally tainted with animus toward Islam," Chief Judge Roger Gregory wrote.

Those appealing the executive order "offer undisputed evidence that the President of the United States has openly and often expressed his desire to ban those of Islamic faith from entering the United States", Gregory wrote.

The latest version of the travel ban blocks people from eight countries - six of which are Muslim-majority - from U.S. entry. It bars immigration from Chad, Iran, Libya, Somalia, Syria and Yemen as well as North Korea and Venezuela.

The Supreme Court is expected to hear arguments in the case in April.

Cecillia Wang, the American Civil Liberties Union's deputy legal director, welcomed the Fourth Circuit Court's decision, claiming it was illegal.

As a candidate running for America's highest office, Trump pledged to enact "a total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what the hell is going on" after several terrorist attacks had occurred in Europe. While in office, he has put out three separate attempts to fulfill the promise but has been dealt successive legal setbacks.

The Supreme Court allowed the third version to go into effect while legal proceedings continued.

Legally speaking, the president, under U.S. Code § 1182 F has almost unlimited authority over immigration.

"Whenever the President finds that the entry of any aliens or of any class of aliens into the United States would be detrimental to the interests of the United States, he may by proclamation, and for such period as he shall deem necessary, suspend the entry of all aliens or any class of aliens as immigrants or nonimmigrants, or impose on the entry of aliens any restrictions he may deem to be appropriate" reads the code.