Presidents have had the power to limit immigration since the inception of this country. Many are aware of the reputation the term "Ellis Island" has, as it's practically ground zero for U.S. immigration. However, the SCOTUS ruling today and justification for their ruling is what should worry you...
I'm sure there are many who oppose immigration from the countries that President Trump outlined in his EO, as many view it is a safeguard from potential terrorist attacks. Those that oppose the EO claim that its prejudicial and that it targets a specific group of people.(Arabs and Muslims)
While I would love to stop terrorist attacks of all kinds, the justification for the SCOTUS ruling should have you worried. Judge Clarence Thomas, joined by Justice Alito and newly christened Justice Neil Gorusch said that, "the government's interest in preserving national security outweighs any hardship to people denied entry into the country."
If you're unaware of what he's saying its simple, the needs of the many outweigh the needs of the few and that the individual, needs to sacrifice for the collective. We've seen this narrative pushed from the left, but its a little harder to identify from the right, as they preach small/limited government, even though they don't always practice it.
He's also saying that we need to sacrifice our rights for safety, something that was continuously pushed by the Obama regime in every facet imaginable, especially when it came to firearms.
The Republicans currently have all the power, and many Republican supporters are still riding the high of an exhilarating and unexpected victory back in November; and after being under Obama for eight years the idea of opposing any politician from the right seems foreign. However, in the last eight years I've seen many Republicans stand up for true limited government and the Constitution, and just because you now have the power to legislate, doesn't mean that stand should end. You should hold the politicians you support to the same, or even higher standard than the politicians you oppose.