Stocks have been on a powerful rally since Trump's improbable victory in the November election. The Dow industrials rallied 7.6 percent from Election Day to the inauguration, the second-strongest move ever, exceeded only by the 21.8 percent Herbert Hoover enjoyed back in 1928-29, which was bolstered by a March inauguration.
Since Trump took office stocks have jumped even higher, with the Dow eclipsing the psychologically significant 20,000 barrier and tacking on about another 2 percentage points on market optimism that he will spur economic growth after eight years of sub-par gains under former President Barack Obama.
But already, the market has shown impatience when it senses Trump is distracted from the job at hand. Therefore, some say his anti-immigration efforts could give investors pause.
"The market looks ahead. But if it looks ahead and sees trouble brewing to get things done, the market is going to perhaps stall until it gets what it wants," Krosby said.
Of course, the market already has had experience with Trump's vagaries, as it went up during one of the most ambitious first weeks in presidential history.
As Trump signed a flurry of executive orders to begin enacting his agenda, he engaged in a heated public battle with Mexico's leadership over the Republican's plan to build a wall on the southern border and force Mexico somehow to pay for it. Through the tumultuous week, the Dow still gained 1.3 percent.
So whether the immigration move will disrupt markets or dampen economic animal spirits will depend on the extent to which Wall Street thinks Trump still can push the domestic agenda while fighting his geopolitical battles.
"What are the market disruptions of not admitting Syrians?" said Peter Morici, a professor at the Robert H. Smith School of Business at the University of Maryland. "This probably is much less of an issue than the media would make it out to be."
Morici acknowledged the "fundamental moral question or trade-off between respecting human rights and protecting the domestic population," but added, "In terms of economic consequences, I can't see a lot."
Strategists and economists on the Street have been raising their projections for the market and growth. But in doing so they almost uniformly cite the same risk: "policy uncertainty" that comes with Trump's unpredictability.