"Exsul Familia" is the apostolic constitution written by Pope Pius XII on the topic of migration. It was released on 1 August 1952. The title of the document refers to the migrant Holy Family, forced to flee into Egypt, taken as the archetype of every refugee family. Exsul Familia is the only papal document, in which Pope Pius himelf outlines the nature and extend of Papal charities during and after the war on millions of refugees and displaced persons.
Exsul Familia is on the millions of refugees after World War Two in Europe. The Pope asked for an open door policy for these millions of stranded people and prescribes pastoral policies for the care of foreign nationals within Roman Catholic dioceses. “We have tried earnestly to produce in the minds of all people a sympathetic approach towards exiles and refugees who are our needier brothers. In fact, we have often spoken of their wretched lives, upheld their rights, and more than once appealed in their behalf to the generosity of all men and especially of Catholics. 
A statistical report from the Council of Europe of that time documents the extend of the problem. In 1950, five years after the end of WWII, there were 11.8 million displaced persons in Europe, of which 1.23 million persons were foreign nationals. This figure has been slightly decreasing since May 1945. Austria and Finland are not included. They add another 801 000 displaced persons. A total of 12.6 million persons lived displaced as refugees in various West European countries. 
The Pontiff views the émigré Holy Family of Nazareth, fleeing into Egypt as the archetype of every refugee family. Therefore, Jesus, Mary and Joseph, living in exile in Egypt to escape the fury of an evil king, are, for all times and all places, the models and protectors of every migrant, alien and refugee. Exsul Familia 1In Exul Familia, Pius XII reviews what the Church has done in this matter and then discusses more fully the implementation of this work in our own times. Experience shows, that displaced persons loose much of their security and human dignity, argued the Pope.
They need special care by the Church. The Church has always done that, by taking care of people in slavery, prisons, deported persons, prisoner colonies, émigrés in the 19th century, and the faithful of the oriental rites. The Pope reviews the charities of his predecessors, of several Catholic aid organizations and gives an interesting detail into the (so far largely undocumented ) charity work during his papacy in WWII. Finally, the Pope explains that many bishops throughout the world have asked the holy see, to issue guidelines for the pastoral care of those who emigrated to their shores. The Second part of Exul Familia contains these guidelines.
Exsul Familia has become the basis for Church immigration policy and has been cited in contemporary political debates about Mexican Catholic immigration to the United States. Migrants are celebrated during the annual World Day of Migrants and Refugees.
St. Ambrose of Milan sacrificed the sacred vessels in order to protect the destitute ones from physical suffering and to relieve them of their pressing spiritual dangers which were even a greater hazard.
- "For who," said Ambrose, is so callous, unfeeling, herd-hearted and cruel that he does not want men saved from death and women from barbarous attacks worse than death? For who is not willing to rescue girls and boys or little children from the service of pagan idols, into which they have been forced under pain of death? We have not undertaken this work without reason; and we have done it openly to proclaim that it is far better to preserve souls for the Lord than to preserve gold. 
- We ourselves desired that the faithful should have an opportunity of going to Confession while travelling by air. We, therefore, later decreed that the permission granted to priests by Canon 883 of the Code of Canon Law, giving faculties for hearing confessions while travelling by sea, should apply also and be extended to priests travelling by air.
- We tried everything possible, striving, urging, entreating, pleading, and appealing directly to the heads of governments to prevent the disastrous war. Even when this tragic war broke out and spread horror throughout the world, we still sought by word and deed to mitigate and restrain it; as much as we could. In these sorrowful circumstances, the Church, as a universal mother, failed neither in her duty nor in what was expected of her. She, the "Head of the universal society of love," became, as was her custom, a comfort for the afflicted, a refuge for the persecuted, a homeland for the exiled.No matter how enormous the difficulties that faced us and how impossible the times, we left nothing untried to bring some aid to our suffering sons, without discrimination as to their status or nationality.
- We also exerted great efforts for the displaced Jews who were victims of the cruelest persecutions. We approved, initiated, and furthered many works of charity for the relief of countless untold wartime disasters and hardships from which practically no one escaped. But in all these works of charity, we were especially solicitous for prisoners of war, refugees, exiles and our other sons who, for whatever reason, had to wander far from their homelands. And along with these, our chief concerns were children and orphans. Yet this being well known to all, since the record is amply documented, there is no need to recount it further. We can however touch on a few specific items.We also appointed a number of other commissions, among them the commission for the victims of war, for civilian refugees and for those detained in custody. This one was later replaced by the Pontifical Commission for Relief for all those who were in need. Equally worthy of mention are the missions arranged by our Secretariate of State and sent more than once into Germany and Austria, chiefly to provide for the welfare of refugees and displaced persons.Then when peace was finally restored, at least in part, the necessity of providing for millions of refugees became daily more urgent. 
- Many of them were prevented from returning to their homes; while at the same time, a large number of other people in many over-populated countries were oppressed by want and had to seek refuge in other lands. Hence, we decided to establish an Office of Migration in the very Secretariae of State itself. It had two sections: one for voluntary migration, the other for enforced deportation. We also delegated an ecclesiastic to the Migration Office established in Geneva so that he might attend international meetings and congresses held in that city.Very recently, we approved the International Catholic Migration Commission, whose function is to unite and organize existing Catholic associations and committees, and to promote, reinforce and coordinate their projects and activities in behalf of migrants and refugees. 
- Nor should we forget to mention how our nuncios and delegates and other ecclesiastics specifically sent to organize committees or commissions for needy refugees and for migrants, successfully founded them in every country, indeed in almost every diocese. This of course, was brought about with the aid of the local bishop and of priests, and of the members of Catholic Action and other apostolic associations as well as other worthy laymen.The diligence and skill of these committees and commissions worthy of our praise achieved many benefits which we ourselves witnessed and which we hope will safeguard migrants and refugees.The war that broke out in Palestine in 1948 brought new reasons for sadness and mourning. Innumerable refugees underwent horrible suffering, being forced to abandon their possessions and to wander throughout Libya, Syria, Jordan, Egypt and the district of Gaza. United in a common disaster, both the rich and the poor, the Christians and the non-Christians, offered a sad and morurnful spectacle.Immediately, following the custom of the Catholic Church to provide assistance for the wretched and the abandoned, we sent as much aid as possible. As was customary in Apostolic times, we specifically established the Pontifical Mission for Palestine, which still relieves the want of Arab refugees through money collected from Catholics everywhere, but particularly through the aid of the special agency established by American bishops, called the Catholic Near East Welfare Association.