WASHINGTON -- Donald Trump has set forth a long list of precedent-setting policy actions he'll take if he's elected president of the United States.
But he rarely, if ever, talks about how he will enact them, seemingly suggesting that he can, like President Obama, simply sign an executive order to achieve his policies with the stroke of a pen.
Build a 10- to 15-foot wall along our 2,000-mile border with Mexico, across often impenetrable terrain, costing at least tens of billions of dollars? No problem.
Knowing Congress will never appropriate the vast sums to pay for Trump's wall, he assured voters from the very beginning that it won't cost taxpayers one red cent. He will simply force Mexico's government to pay for all of it -- even though Mexican officials, from the president on down, have said that will never happen.
Yes it will, Trump says, because if they refuse, he will, supposedly with the stroke of the pen, intercept the money sent by Hispanics to families and relatives back home, estimated in the billions of dollars. That will wreak havoc with Mexico's economy, which depends on this infusion of cash, and in the end, the country will cry uncle and agree to pay the bill. In his dreams.
But what legislative role does the Congress play in all of this? Can any president unilaterally order the confiscation of cash transfers by U.S. citizens, or from migrants who are here legally under work permits, or even illegals? That seems unconstitutional on the face of it, but the Donald has never explained how he would go about doing this, and his supporters aren't questioning its legality.
It should be crystal clear by now that the Congress has sole authority over our immigration laws. But ever since its 2006 approval of a failed 700-mile, $2.5 billion fence along the Rio Grande, Congress has shown little interest in building a wall along our entire border.
The Wall Street Journal warned at the time that the idea of constructing a double-layered fence would turn out to be a huge, costly and ineffective "boondoggle." And that, according to Trump's campaign speeches, is exactly what happened.
So what makes him think his huge concrete wall will be more effective? Does he think no one will come in via the West Coast?
And what about Trump's plan to deport 11 to 12 million illegal migrants? Obviously, the executive branch does not possess the singular constitutional authority to authorize a nationwide roundup of such magnitude, nor to pay for its massive costs without Congress' approval.
The last time Congress tackled this issue, the pending legislation was focused on giving illegal migrants a path to becoming legal and, eventually, citizens. The bipartisan bill went nowhere.
It seems unlikely that a President Trump would be able to persuade Congress to do a complete about-face on this issue after years of debate, and countless votes that never seriously considered mass deportation.
And what about his intention to raise trade tariffs by 45 percent on foreign imports to reduce the trade deficit?
A tariff is a tax, like any other, that our trading partners pay to send their products into our country. Trump's tariffs have long been championed by left-wing Democratic union leaders, the very people who are helping to bankroll Hillary Clinton's presidential campaign and her get-out-the-vote effort in November.
Economists and business leaders are warning that if Trump's tariffs were ever to become law in the U.S., prices in Wal-Mart, Target and other cost-cutting stores, where low- to middle-income Americans shop, would triple.
But Congress is the sole arbiter of trade policy, and as long as the GOP controls Congress, any proposal to raise tariffs would be dead on arrival.
What all this suggests is that the only thing that stands between Trump's authoritarian presidency and the rule of law is Congress.
Over the course of the past year or more, that's not a word you heard much in Trump's bombastic speeches. He will build the wall and make a sovereign country pay for it against its will. He will deport millions of illegal migrants on his own authority. He will hike tariffs on imported goods, giving union bosses the No. 1 tax on their wish list and higher prices for struggling Americans trying to make ends meet.
Trump seems to look upon that shining domed building on Capitol Hill as an institution that will play little or no part in his plans for America.
He has met with its GOP leadership, at their invitation, but only to hear their deep concerns and grievances about his agenda and his insulting, bullying behavior toward anyone who disagrees with him.
But as troubling questions persist about Trump, and as he gets closer to the possibility of sitting in the Oval Office, Capitol Hill looms as an insurmountable wall between him and policies that would hurt our country and its economy.
America has been blessed over the course of its history, choosing presidents who possessed the "temperament, stability, judgment and compassion to occupy the office," to quote columnist Michael Gerson.
But in case the voters chose someone who would inflict great harm to America's principles, the Founding Fathers wisely created a system ruled by three wholly independent branches of government.
In such cases, Congress and, if necessary, the Supreme Court stand ready to ensure that such a president would not be allowed to exercise his authority without the consent of the governed. Donald Trump still seems to have trouble understanding that.