(Reuters) – The arrest in Canada of a top Chinese technology executive for possible extradition to the United States has roiled markets and cast doubt on a recent U.S.-China trade truce.

Huawei Technologies Co Ltd Chief Financial Officer Meng Wanzhou, who is also the daughter of the telecommunications company’s founder, was detained on Saturday while changing planes in Vancouver. A person familiar with the matter told Reuters she faces extradition on charges related to U.S. sanctions violations.

Chinese authorities have criticized the United States and Canada, saying they did not explain why Meng was arrested and demanded her release.

These are steps that U.S. authorities typically follow in seeking arrests and extraditions of individuals in foreign countries.

How do U.S. authorities arrange arrests in foreign countries?

Federal and state prosecutors in the United States cannot simply request that their foreign counterparts arrest and turn over an individual. Such requests must be made through the U.S. Department of Justice’s Office of International Affairs (OIA).

The OIA maintains lines of communication with authorities in other countries, and is responsible for taking the next steps leading to an arrest and an extradition.

Douglas McNabb, a Houston-based international criminal defense lawyer, said the decision to pursue charges against someone like Meng could have been made at senior U.S. government levels, “given the circumstances that she is a Chinese citizen whose father has significant authority in the state.”

Bradley Simon, a criminal defense lawyer and a former federal prosecutor in Brooklyn, said a move against someone like Meng probably involved “extra scrutiny up the chain of command” at the Justice Department.

How do extraditions from Canada to the United States work?

Canada is one of the more than 100 countries with which the United States has extradition treaties, obligating it to cooperate with OIA requests. These treaties vary by the offenses covered, and some exclude a nation’s own citizens or anyone facing capital punishment.

The longstanding U.S.-Canada treaty requires the offense for which extradition is sought to be a crime in both countries.

It is not clear if OIA has formally requested Meng’s extradition.

Once a request is received, a Canadian court must determine if there is sufficient evidence to support extradition and Canada’s Minister of Justice must give a formal order.

What about countries with no extradition treaty?

China, Russia and Saudi Arabia are among the nations with no U.S. extradition treaties.

If a U.S. target is in one those countries, one option for OIA is to contact Interpol to put out a so-called red notice indicating there is an outstanding arrest warrant for that person.

Red notices are not typically made public, but a person may be arrested on the basis of a red notice as soon as that person arrives at a border crossing or airport in a third country that does have an extradition treaty with the United States.

Meng was arrested at an airport, but Reuters has not confirmed if Canada arrested her pursuant to a red notice.

Can Meng fight extradition to the United States?

OIA requests for extradition differ by treaty but generally require U.S. authorities to document the nature of the charges and the evidence.

Defendants have typically fought extradition on the grounds that their rights in the arresting country would be violated if they were sent to the requesting country to face legal proceedings. Some previous fights have lasted for months or even years.

Could politics have played a role in Meng’s arrest?

The timing of Meng’s arrest, coinciding with trade negotiations between U.S. President Donald Trump and Chinese President Xi Jinping, has some observers speculating about a possible political motivation.

A White House official said on Thursday that Trump did not know about any request for Meng’s extradition at the time he met with Xi over dinner on Saturday, the day of the arrest.

Simon said the president has no authority to order the prosecution of an individual and any case against Meng would have been subject to “many levels” of review within the Justice Department before moving forward. He also said her arrest in transit in Canada seemed opportunistic rather than calculated.

But Simon said it was possible the Justice Department consulted the White House on timing, given the political concerns or sensitivities.