Traveling or returning to the U.S. from abroad has become increasingly risky for some — even for people with valid visas and green cards.

In recent weeks, international tourists, visa holders and lawful permanent residents — also known as green-card holders — have been facing tougher scrutiny at airports and border crossings. The change comes amid a broader crackdown by the Trump administration to reduce both legal and illegal immigration to the country.

And as spring break trips and summer vacations draw near, stories of green-card and visa holders being detained have sparked new concerns about traveling.

Earlier this month, for example, Brown University urged its international staff and students to postpone any plans to travel outside the U.S. “out of an abundance of caution.” Canada, along with several countries in Europe, including Denmark, Ireland and Germany, have also updated their travel guidance for the U.S., urging their citizens to strictly adhere to U.S. entry rules or risk detention.

In a statement to NPR, Hilton Beckham, assistant commissioner of U.S. Customs and Border Protection (CBP), said, “Green card holders who have not broken any U.S. laws, committed application fraud, or failed to apply for a re-entry permit after a long period of travel have nothing to fear about entering and exiting the country.”

Immigration attorneys told NPR the riskiness of traveling abroad will be different for individual travelers, making it important for them to understand their rights and privileges before making travel plans.

Here’s what to know.

Get up to speed on your rights based on your status

There are generally three kinds of travelers who enter the U.S., according to Stephanie Gee, senior director of U.S. legal services at the International Refugee Assistance Project (IRAP).

U.S. citizens have guaranteed access to the country, Gee said. Green-card holders have procedural rights, meaning only an immigration judge can revoke their green card status. That means U.S. citizens and green-card holders can choose to not answer CBP officers’ questions or let them search their electronic devices, though refusing to do so can result in a delay in entry.

On the other hand, travelers with a temporary visa, which is common among students and tourists, have the “fewest rights,” Gee said. CBP officers have the final say on whether these travelers can enter the country, and can simply deny entry if a visa holder refuses to answer officers’ questions.

Stephen Yale-Loehr, a retired immigration law professor from Cornell Law School, recommends that green-card and visa holders double check their immigration documents before they fly.

“Make sure everything is in order, their visa hasn’t expired or they don’t have a renewal application pending,” he said.

Assess your risk level, preferably with an immigration attorney

There are additional factors that could raise a traveler’s risk level. Yale-Loehr pointed to a draft list of 43 countries that could be hit with a new travel ban, as reported by The New York Times earlier this month. (NPR has not independently confirmed the reporting.)

Though there’s not a list that’s currently in effect, Yale-Loehr advised that travelers from the 11 countries in the proposed “red” category — places where travel to the U.S. would be banned outright — should think twice before flying here. These countries include Afghanistan, Bhutan, Cuba, Iran, Libya, North Korea, Somalia, Sudan, Syria, Venezuela and Yemen.

Yale-Loehr added that typically, visa holders who are denied entry are simply put on the next plane back to their home country. But some people have recently been taken into custody and detained for days and weeks on end. “ It’s a seemingly a growing problem,” he said.

For green-card holders, factors like a long trip abroad can raise suspicion at the airport. Lately, some immigration attorneys have also been warning that green-card holders with a criminal record, no matter how minor, should avoid leaving the country.

In a recent case earlier this month, 34-year-old electrical engineer Fabian Schmidt, a green-card holder originally from Germany, was taken to immigration detention from Logan International Airport in Boston over a decade-old misdemeanor charge for marijuana possession.

Gee from IRAP said the best practice is for green-card and visa holders to consult an immigration attorney and get tailored advice on their personal situation.

“Even if this is not something you would’ve considered doing and you’ve traveled routinely before,” she said. “Just because its clear that immigration enforcement at airports is picking up in a way that it has not in the past.”

Know that customs officers are allowed to search your electronic devices

CBP officers can ask travelers to unlock their cell phones, give laptop passwords or hand over digital cameras. U.S. citizens and green-card holders can’t be turned away simply because they refuse, but visa holders can, according to Yale-Loehr.

He said during an electronic search, CBP officers often look for material that would suggest non-citizens are ineligible to enter the U.S. That includes criminal convictions, domestic violence and support of terrorism.

“ There’s wide discretion at the border in terms of who to admit to the United States, even if you have a valid visa,” Yale-Loehr said.

If a traveler’s electronic device gets confiscated, the American Civil Liberties Union suggests asking for the officers’ names, badge numbers and which agency they work for. It also advises that travelers should call the agency to request a receipt documenting that a personal item was taken away.

Alert a trusted friend if things go awry

According to the ACLU, travelers who are asked to undergo further inspection at the airport are not entitled to an attorney.

Yale-Loehr said it’s still useful to have an immigration attorney’s contact information on hand. He also suggests travelers to have a friend who can be quickly reached if there’s trouble entering the U.S.

“So if it looks like you’re going to be questioned by the border people, you can text a friend saying, ‘I’m being pulled into secondary inspection, contact my immigration lawyer,’ ” he said.

Gee from IRAP added that travelers can also ask for an interpreter if they need language assistance during inspections.

“That’s really important actually because the questions you’re being asked and your answers to them are really going to determine — a lot of times — the outcome of that situation,” she said. “So you should not be shy about saying, ‘I don’t understand. I need an interpreter.’ If that’s your situation.”

Even if authorities do not provide an interpreter, Gee said it’s helpful to have the request on the record.

 ”There’s generally going to be a transcript of the questions and answers in these types of interviews and inspections, and that is the kind of official record of what actually happens during this time,” she said.

NPR’s Joel Rose contributed to this story.