President-elect Donald Trump has laid out an ambitious agenda for when he takes office, including plans for a wall along the Mexican border, pricey tariffs on some foreign goods and a possible ban on Muslim immigrants.

But the next leader of the free world could face considerable resistance in implementing some of these proposals — particularly from members of his own party.

Much of his campaign rhetoric called for the elimination of policies and treaties proposed or enacted under the Obama administration. These include the Trans-Pacific Partnership trade deal, Obamacare, the Iran nuclear deal, the Paris agreement on climate change, as well as a renegotiation or exit from NAFTA.

As for what policies a Trump administration would implement, some are outlined in his 100-day action plan released in October — "Donald Trump's Contract with the American Voter."

Tax cuts

Trump might begin with his plan to cut taxes, a measure that will likely receive support from the Republican-dominated Senate and House, and particularly House Speaker Paul Ryan.

Despite tensions between the two, Trump and House Speaker Paul Ryan might find common ground on tax cuts. (Alex Brandon/Associated Press)

While there's no love lost between Ryan and Trump, this is one area where the two could find common ground. While they agree on the merits of tax reductions, they might differ on how much to cut.

According to the Tax Policy Center, Trump proposed cutting taxes by $6.2 trillion over 10 years — twice the size of the House Republican plan. And as the centre points out, it's unlikely a Republican-dominated Congress would approve a plan that's projected to increase the national debt by $7 trillion over the next decade.

The Wall

To combat illegal immigration, Trump has proposed the construction of a wall that's 1,600 kilometres long and 12 metres high along the U.S. border with Mexico.

The project would face a few major obstacles.

First, there would be legal challenges from property owners because much of the wall would need to be built on private property, says John Sides, an associate professor of political science at George Washington University.

Then there's the cost. Trump has estimated a price tag of around $10 billion, while others have suggested it could range from $15 billion to $25 billion, or possibly $40 billion.

A U.S. Border Patrol agent drives near the U.S.-Mexico border fence in Santa Teresa, N.M. Trump has proposed a wall along the border to prevent illegal immigration. (Russell Contreras/Associated Press)

Trump has said Mexico will pay for this barrier. But if his legendary deal-making abilities aren't able to swing that, it will be up to Congress to appropriate the money. And budget-conscious members of his own party might not be so eager to pony up for this endeavour.

Rey Koslowski, associate professor of political science at the University at Albany, says the economies of states like California, Texas and Arizona depend on a strong trade relationship with Mexico. He says those businesses, many of which support Republican members of Congress, don't want the government spending money on walls or any other policies that could hurt their bottom line.

Plus, as Sides points out, Trump would likely need a supermajority in the Senate — 2/3 support, meaning more than just Republican votes — to get it funded.

"I doubt that Congress will rubber-stamp this."

Deportation of illegal immigrants

Trump's vow to crackdown on the estimated 11 million illegal immigrants in the U.S would be difficult, expensive and politically risky, according to Koslowski and Sides.

"The issue is just the capacity to identify, apprehend, and then process and deport," Koslowski said.

"It is a massive and expensive undertaking," Sides added. "Perhaps he could authorize this unilaterally, but it would soon strain the capabilities of law enforcement. There would also be a huge political backlash."

Muslim ban?

Trump's contract with voters also includes the pledge to "suspend immigration from terror-prone regions where vetting cannot safely occur" — a refinement of his earlier promise of a "total and complete shutdown of Muslims entering the United States."

Constitutional scholars have expressed mixed opinions on whether that would be unconstitutional. Yet by tweaking the wording of his ban to replace "Muslims" with "immigration from terror-prone regions," Trump may have the authority he needs.

A woman wearing a Muslim headscarf walks past Trump supporters before the annual Muslim Day Parade in the Manhattan on Sept. 25. (Stephanie Keith/Reuters)

As pointed out in the New York Times, Trump's ban would rely on a law that gives the president authority to prevent the entry of any class of people who would be "detrimental to the interests of the United States."

Gary Gregg, director of the University of Louisville's McConnell Center, says whether Trump decides to push the initiative will depend on what's happening at home and abroad.

"If we're quiet, as we have been, there will be no incentive to bring it up and to force that issue, which will poison the well," he said. "But if there are some terrorist attacks, the game changes at that point and that will be on the public's mind, his supporters' minds and likely on his mind."

"My guess is he will be around smart enough people ... who will say, 'You don't want to start off with doing the most controversial thing you can do."

Tariffs

Trump vowed in the campaign to slap a 35 per cent tariff on goods coming from Mexico and a 45 per cent tariff on Chinese imports. Free-trade Republicans in the House and Senate likely wouldn't support such a move. But would Trump even need congressional approval to take action? Apparently not.

Gary Hufbauer, a senior fellow at the Peterson Institute for International Economics, says Trump's targeted tariffs would fall within his presidential powers.

"He can be very specific on what products he targets. So if there's a particular company that he thinks is moving jobs to Mexico and he wants to penalize them ... he can target those particular products. He's got a lot of power."

Trump, seen here with Senate majority leader Mitch McConnell, might find that Republicans aren't so keen to endorse some of his proposals, such as new tariffs on products from Mexico and China. (The Associated Press)

But Trump would be restrained, Hufbauer says, by the economic blowback of such measures. Tariffs like those would affect U.S firms that are dependent on certain imports to make their products. It could force them to shut down their lines and lay off workers.

And foreign countries will retaliate, he says, targeting products from states that are politically sensitive for the president.

"That blowback impact ... would cause a President Trump to pause, but he has all the legal authority he needs to do these things."