Elon Musk briefly worked illegally in the US after abandoning a graduate studies program in California, according to a Washington Post report that contrasted the episode with the South African multibillionaire’s anti-immigration views.

The boss of Tesla and SpaceX, who has in recent weeks supported Donald Trump’s campaign for a second presidency while promoting the Republican White House nominee’s opposition to “open borders” on his X social media site, has previously maintained that his transition from student to entrepreneur was a “legal grey area”.

But the Washington Post reported Saturday that the world’s wealthiest individual was almost certainly working in the US without correct authorization for a period in 1995 after he dropped out of Stanford University to work on his debut company, Zip2, which sold for about $300m four years later.

Legal experts said foreign students cannot drop out of school to build a company even if they are not getting paid. The Post also noted that – prior to the September 11 terrorist attacks agains the US in 2001 – regulation for student visas was more lax.

“If you do anything that helps to facilitate revenue creation, such as design code or try to make sales in furtherance of revenue creation, then you’re in trouble,” Leon Fresco, a former US justice department immigration litigator, told the outlet.

But the Post also acknowledged: “While overstaying a student visa is somewhat common and officials have at times turned a blind eye to it, it remains illegal.”

Musk has previously said: “I was legally there, but I was meant to be doing student work. I was allowed to do work sort of supporting whatever.”

Musk employs 121,000 people at Tesla, about 13,000 at SpaceX and nearly 3,000 at X. The scrutiny of his immigration status after dropping out of Stanford comes after Trump has touted his desire for Musk to play a high-profile role focused on government efficiency in a second Trump administration if voters return him to office at the expense of Kamala Harris in the 5 November election.

Musk in turn has accused the vice-president and her fellow Democrats of “importing voters” through illegal and temporary protected status immigration. During a recent Trump campaign appearance, he compared the US-Mexico border to a “zombie apocalypse” – even as he had also previously described himself as “extremely pro immigrant, being one myself”.

Bloomberg News recently published an analysis of more than 53,000 posts sent from Musk’s X account, finding that the entrepreneur’s output turned increasingly political this election year.

“In 2024, immigration and voter fraud has become Musk’s most frequently posted and engaged with policy topic, garnering about 10bn views,” the outlet said. “Musk posted more than 1,300 times about the topic overall, with more than 330 posts in the past 2 months alone.”

Bloomberg described Musk – who paid $44bn for X, then Twitter, in 2022 – as the platform’s single most important influencer and has reportedly ordered site engineers to push his posts into users’ feeds. That makes Musk “the most widely read person on the site today”, Bloomberg said.