But as growing numbers of Africans scale the barriers, Spanish officials have adopted a different strategy, one that appears to challenge European Union law: Paramilitary police, in stepped-up patrols, are deporting some fence jumpers as they drop into the enclaves.

EU law bars summary deportations and requires members to allow anyone who steps foot on their territory to apply for political asylum.

Spain is trying to finesse that requirement by declaring a "security perimeter" on the Spanish side of the border fences. It is no longer enough, it says, to clamber up the fences and tumble onto Spanish soil to be assured of an asylum hearing.

Instead, it claims, migrants detained in this zone can immediately be sent back to Morocco without a hearing. Authorities have proposed an amendment to Spain's national-security law that would retroactively legalize this practice, which border police say has become routine.

The shift is part of a hardening stance against illegal immigration by Southern European countries as mounting turmoil from Syria to Libya and violence and oppression in Africa uproot and drive thousands of people toward the Continent. It reflects a preference by some European governments to assert national control over regional bodies on contentious matters of migration policy.

Greece has drawn criticism from EU officials for building a 6-mile-long fence along its land border with Turkey to keep out migrants. Nils Muiznieks, commissioner for human rights at the Council of Europe, the Continent's leading human-rights organization, said Italy, Greece and Bulgaria have violated EU law by recently pushing back migrants, an allegation Athens denies. Italian and Bulgarian officials didn't respond immediately to requests to comment.

Spain, Mr. Muiznieks added, is the only European country attempting to legalize the practice.

In the U.S., border agents sometimes informally encourage immigrants to turn around when they encounter them at the border—an alternative to the more common procedure of detention, processing and initiating deportation proceedings.

Under U.S. law, any person apprehended at the border who isn't legally allowed entry into the U.S. can be deported by the U.S. Department of Homeland Security without an appearance before an immigration judge or the opportunity to retain legal counsel. Only a well-founded fear of political or religious persecution can avert immediate deportation.

Spanish officials say they are fighting a rising tide of migrants who are being funneled toward their North African enclaves by trafficking organizations wary of riskier crossings of the Mediterranean Sea. The enclaves, Ceuta and Melilla, make Spain the only European country whose territory has a land border with the African continent.

In the first nine months of this year, more than 5,000 people fleeing African countries have journeyed to Morocco, dodged police there, and scaled three parallel rows of fences to reach the two enclaves, according to the office of the United Nations High Commissioner for Refugees.

That is double the number who had entered the enclaves illegally in the year-earlier period.

Groups of up to 300 migrants have stormed the border at once, some using rock-climbing hooks to scale the tallest fences, which are 20 feet. In videos released by Spanish police, some fence jumpers shout that they are infected with Ebola and spit at officers in an effort to avoid detention.

Few migrants reaching the enclaves gain asylum, but even most of those who fail are allowed to remain there or move to the European mainland, since few African countries have repatriation treaties with Spain.

"The way this works, you spend some time here, and then they let you go to Europe," said Abu Bakr, a 20-year-old migrant from Guinea who jumped the fence into Melilla two months ago.

Abdelmalik El Barkani, the head of Melilla's local government, said the influx had become intolerable. "We can't resign ourselves to an immigration system that works along these lines," he said. "We're fine with immigration, but not like this."

Spain's practice of summary deportation came to light last month when an edited video released by Prodein, a Spanish group that advocates for immigrant rights, showed police in Melilla beating a 23-year-old fence jumper from Cameroon and carrying him back into Morocco.A fuller version of the video, later released by Spanish police, showed that the man had first swung a climbing hook at officers who were trying to apprehend him.Police say such incidents are common and that selective evictions of fence jumpers have been going on for months.

Speaking in the Spanish parliament last month, Interior Minister Jorge Fernández Díaz said the amendment was necessary to protect officers from possible legal action by critics of their border enforcement methods. It would outline a legal concept he called "rejection on the border" and distinguish it from summary deportation.

Spain's ruling Popular Party has enough votes to get the amendment approved, but the Council of Europe and the U.N. refugee agency say it would violate international law and EU law. Mr. Muiznieks of the Council of Europe said it would likely be struck down by Spanish courts or the European Court of Human Rights.

"You can't square this law with Spain's international commitments and treaties," he said.

EIN.News