(CNN) When Sean Binder arrived on the Greek island of Lesbos in October 2017, the migrant crisis facing Europe had changed from a temporary emergency to a long-term political reality. While the number of crossings had dropped dramatically since 2015, deaths at sea remained high , and those surviving the journey were facing indefinite stays in overcrowded camps on arrival.

As a trained rescue diver, Binder travelled from Ireland to Lesbos to volunteer with the non-profit organization Emergency Response Centre International. "I helped on rescue efforts on the southern shore. During our operations we worked closely with the Greek authorities -- the coast guard," he tells CNN.

Yet despite working alongside local authorities for almost a year, Binder, along with two fellow search and rescue volunteers, was arrested for his aid work in August 2018. "It was 3am. We were looking out in case there was an arrival and that's when the police came to arrest us."

He was placed in pre-trial detention on the Greek Island of Chios, where he spent nearly four months in a small prison while police investigated his case. Binder was released on bail in December 2018, while the investigation continues. He still faces a number of serious charges. "The most outrageous are; being part of a criminal organization, money laundering, smuggling... and espionage or spying," Binder tells CNN.

If found guilty, he could spend up to 25 years in prison, however Binder is adamant that authorities aren't looking to convict him.

"Despite the aggressive nature of the charges, there is no real will to prosecute and that's because there's insufficient evidence to actually do so," he explains.

"For instance I'm accused of being a spy, and that's because I used communication services that are encrypted. Which sounds nefarious, but what they don't allude to, is that it's WhatsApp."

Sean Binder believes the charges against him are aimed at deterring other aid workers from taking part in vital search and rescue operations at sea.

The real reason for the charges, Binder believes, is to deter other aid workers from taking part in vital search and rescue operations at sea.

"The effect has been to embroil us in costly and lengthy legal procedures and this acts as a form of deterrence. When we worked on the southern shore of Lesbos, we were one of three or four organizations. There are now none of them," he says.

"This has been the effect. It's frightened people away from doing this kind of work."

In December, Binder will appear in court to find out whether the judicial council in Lesbos plans to indict him. Until that happens, he remains the subject of an ongoing investigation. Under Greek law, the prosecutor overseeing this case is prohibited from commenting on the charges.

CNN has contacted the Greek government for comment regarding the investigation. As yet, there has been no response.

A wider crackdown is taking place against aid workers and good Samaritans across Europe.

Wider crackdown

Binder's case is not isolated. Rather, it is part of a wider crackdown against aid workers and good Samaritans taking place across Europe.

In June, an EU-funded research paper found that since the height of Europe's migrant crisis in 2015, at least 158 individuals have been "investigated or formally prosecuted on grounds of smuggling and other grounds... such as money laundering, membership of a criminal organisation and sabotage". It also found at least 16 NGOs have been affected by the investigations of their volunteers.

One of the most prominent cases this year occurred in June, when German Sea-Watch Captain Carola Rackete defied Italian authorities by disembarking her ship in the port of Lampedusa with 40 rescued migrants on board. The boat had been stranded in the Mediterranean for more than two weeks before docking in the Italian port without permission.

Rackete was then arrested for aiding illegal migration and entering a port without permission. Some of the charges have since been dropped, but she still faces an ongoing investigation under people-smuggling laws.

Rackete says cases like hers will continue, unless there's public pressure.

"I don't see their policies changing until civil society in Europe steps up and confronts them. Right now, the EU is intent on being perceived as the good guy, holding up human rights... but we are criminalizing human beings helping other human beings in need," she tells CNN.

German Sea-Watch Captain Carola Rackete defied Italian authorities by docking with 40 rescued migrants on board.

A successful deterrent

According to the European Union's Agency for Fundamental Rights (FRA), these cases are successfully serving as a deterrent.

In a note published in October 2018 , and updated in June 2019 , the FRA found "the recent trend of initiating criminal proceedings against non-governmental organisations (NGOs) or other private entities deploying rescue vessels... resulted in most NGOs stopping their operations by the end of 2018." The FRA also acknowledged that this trend is taking place while "deaths at sea remain high."

Lawyers and academics say that by pursuing cases against aid organizations, EU member states are exploiting a loophole in what is known as the "Facilitation Directive." Put in place in 2002, the directive acts as the EU's main framework for cracking down on people-smugglers.

In its current form, the directive allows member states to prosecute anyone who helps a migrant enter Europe illegally. There is no guaranteed protection for humanitarian workers written into the document and it doesn't stipulate that financial gain must be involved in order to charge someone with smuggling.

An inflatable dinghy, belonging to the "Ocean Viking" rescue ship, operated by French NGOs SOS Mediterranee and Medecins sans Frontieres (MSF), rescues migrants in the Mediterranean in August 2019.

This is in stark contrast to the UN Smuggling Protocol, and violates basic principles of International Humanitarian Law. Legal experts even argue that the Facilitation Directive has created uncertainty over what is and what is not a crime of migrant smuggling.

Paula Schmid Porras is a human rights lawyer who has represented several volunteers who have been arrested while rescuing migrants.

In 2016, she petitioned the EU Parliament to reword and clarify the directive to close the loopholes.

"The response of the former European Parliament's legislature was receptive," she tells CNN.

"MEPs from the most representative political parties understood that it's unacceptable that European citizens can be prosecuted for helping humans in need."

A group of 47 migrants is helped by a Sea Watch 3 crew member (left) during a rescue operation off Libya in January 2019.

Porras says the initial momentum to overhaul the directive stalled following the success of far-right parties in the European elections this year.

"The amending process should have started one year ago, but the European elections stopped the process," she explains.

Porras says members of the EU Parliament's Committee on Civil Liberties, Justice and Home Affairs are still working to amend these laws, but "sadly, the implicit xenophobia of the far-right MEPs is blocking the cause."

The European Union has commissioned several studies to examine the Facilitation Directive, dating back to 2016

Consistently, the research recommends that "legislative change is needed to bring the EU legislation and policies in line with international, regional and EU criminal justice and fundamental rights standards."

In 2017, the European Commission undertook its own assessment of the directive. Despite evaluating evidence of its misuse, the Commission refrained from making any amendments. The latest analysis of the directive by the Centre for European Policy Studies on request of the European Parliament published in January this year reiterated that it "stands at odds with the EU's founding values" and recommended full legislative change/update "to prohibit the criminalisation of humanitarian assistance."

In a statement to CNN, a European Commission spokeswoman acknowledged there "is a lack of clarity in the implementation of the humanitarian exemption clause" in the directive, and that the EU continues to "gather evidence" about how these laws are being applied.