Nazanin Zinouri is a data scientist in Greenville, S.C., with a doctorate in industrial engineering from Clemson University.
Protesters in cities across the nation rallied against President Trump's executive order banning U.S. entry for refugees, migrants and foreign nationals for 120 days. Here's a look at some of the protests that took place in airports and city squares across the U.S. after the order was signed. (Dalton Bennett,Erin Patrick O'Connor,Elyse Samuels,Monica Akhtar/The Washington Post)

TEHRAN — On Thursday night, I looked at the news while visiting my family here and realized I had a problem. President Trump would be signing executive orders the next day. One of them would ban me from returning to my home in Greenville, S.C., and it did cause federal agents to block me from my flight from Dubai to Washington on Friday night.

I’ve lived in South Carolina since 2013, when I started my doctoral studies in industrial engineering at Clemson University. I was born in a middle-class family in Tehran, raised by parents who taught me to love and respect people regardless of their race, religion or background. I learned to value education for its contributions to community life, its role in advancing social justice, its capacity to open worlds of cultural and artistic excellence — for the way it helps humanity flourish.

My passion for mathematics and problem-solving had started as a young girl. I studied hard for years and did well in Iran’s mandatory university entrance exam. I won a full scholarship to study engineering at one of the country’s best universities. My dream was to go to the United States for graduate school. Professors and departments at U.S. universities were renowned even in Iran. And I’d heard from friends who lived there how nice Americans were, how warmly they welcomed immigrants. I was admitted to several masters programs and decided to attend Northern Illinois University, which offered another full scholarship.

Before I could start, I had to get a student visa. There’s no U.S. diplomatic presence in Iran, so I had to make an expensive trip to Turkey for an interview. My application required additional security checks, but I understood: That’s typical for Iranian citizens, and obviously, any country needs to be sure the people they allow in aren’t a threat. Finally, on Aug. 13, 2010, I entered the United States for the first time.

In May 2013, once I graduated from my master’s program, I went to Iran to see my family for the first time in three years. I had to apply for a new visa, but it was worth the hassle; I had dedicated my life in the United States to academics, and knew I’d clear the background checks again. I couldn’t bear to stay away any longer.

All through the summer of 2013, I waited in Tehran for my new visa so I could move to Greenville to start my PhD at Clemson. It came through, and I returned to the United States that August. I promised myself I’d return to Iran once a year to see my sister and mother, who had been left without help when my father died. In 2014, I finally got a visa that was good for multiple entries, which meant I could visit home without bureaucracy getting in the way. In August, I graduated and found a job as a data scientist at a technology firm in Greenville, under a provision in the law that allows students to work on their student visas for a time after graduating.

I love my job and the team I work with. My firm started the process to sponsor me for a green card, which would give me permanent legal residence and put me on the path to becoming a U.S. citizen. In August, I adopted a rescue puppy who’d gone unwanted because of his gastrointestinal issues. I named him Dexter. He’s adorable. I became close friends with three women in my neighborhood, and we walk our dogs together every morning and evening. I love downtown Greenville, which was especially pretty when it was decorated for Christmas. (There’s even a Persian restaurant for when I want a little taste of Tehran.) My life in upstate South Carolina has been very peaceful.

In the winter, I decided to take a three-week trip to visit my mom and sister. My visa was in order, but I hauled along a ton of paperwork to avoid trouble — I had my job offer letter, my employment authorization form, multiple pay stubs, even copies of my old student visas, just in case. I got to Tehran on Jan. 22.

Within two days, the rumors about Trump’s executive orders were flying. It was shocking: How could the United States I know and love — a country based on the rule of law, where supporting human rights is foundational — ban people just because they come from Muslim nations?

When I saw the news that Trump was really going to go through with the order, I realized I had to leave immediately, three days into my trip. The first available flight back to the United States would take me through Dubai on Friday and then to Dulles International Airport. Trump signed the order before I boarded in Tehran. When I got to Dubai, U.S. border agents based there asked me lots of questions, as they usually do. This time, they asked why I was going back on a student visa since I had graduated (even though my visa allows me to work after school). They let me through at first.

But later, when passengers started to line up to board, airline employees and the U.S. officials started talking. They looked at me several times. I knew about the order, and I was getting more and more nervous. Finally, it happened: Someone walked over to me and said due to “security reasons,” I had been denied boarding, and I had to leave the line.

I didn’t ask anything. I couldn’t talk. I was dizzy, and everything got blurry. I just walked away from the gate as early as I could. I didn’t see any other Iranians among the passengers. I am guessing no one from the other six banned countries was there, either, or at least no one with a visa. Because I didn’t see anyone else getting removed.

People were watching. Some passengers were frustrated that the boarding process was getting delayed. It might have been embarrassing, in other circumstances, but I was just numb. A million thoughts rushed through my mind, from the practical to the philosophical: What happens to Dexter now? He is waiting for his mom to come home. Who is going to take him for doctor visits? What happens to my car parked at the long-term lot at the Atlanta airport? What happens to all the stuff I had collected during 6½ years living in the United States? What about my lease? Will my landlord think I just left town? What happens to my job, my life, my American Dream? I flew back to Tehran to stay with my family and figure out what to do next, stung by the realization that as far as the U.S. government is concerned, my life doesn’t matter. Nothing I worked for all these years matters.

I have applied for a visa three times and have been through extensive clearance and vetting every time. And every time I have been cleared and received my visa. My documents were again evaluated by the Department of Homeland Security when I applied for a work authorization. So I think I have been through vetting enough times. How does it make sense to keep me from going back to where I live because I need “extreme vetting?”

I still consider America to be where my home is. I’ve spent my whole adult life there. I have lots of friends; some of them are like family to me. I still love the nice Americans who welcomed me to their country. Of course, I have concerns now about whether the safety and peace I found there will change, but I still love America. I want to go back.