Donald Trump has been President for just three days but there's already a petition calling for his impeachment.

LISTEN ABOVE: USA Today correspondent Paul Singer speaks to Rachel Smalley

The controversial billionaire and reality TV star has taken over the White House after being sworn in as the 45th president of the United States on Saturday (NZT).

More than 100,000 people have signed the petition calling for impeachment so far, arguing his business conflicts of interest make him ineligible to serve as President.

However, a law professor says it's unlikely any amount of signatures could actually make it happen, despite the certain controversies of a Trump presidency.

READ MORE: New administration continues tenuous relationship with truth

Waikato University law professor Alexander Gillespie said impeachment is easier said than done and said Bill Clinton's impeachment trial shows how difficult it is to get both houses of Congress to consent to removing a sitting president.

"In theory he could lose power by an indictment of congress [but] in reality, it's very rare congress would cooperate on the indictment of a president," he said.

It won't all be smooth sailing though - Gillespie said all eyes will be on President Trump's business interests.

He said setting up a blind trust may be the only way for Trump to shake off conflict of interest allegations.

Trump is dealing with several countries where he has business interests and Gillespie says he needs to disinvest or put all his investments into a blind trust.

"People will continually be asking, is he making that decision because it's the right thing to do for America or is he doing it because it's the right thing to do for his hotel interest in Manila?"