ABOARD THE PAPAL PLANE — After a day of touting ways in which Christians might share in greater unity, that commitment to coming together didn’t prevent Pope Francis from backing the Vatican’s doctrinal watchdog in its decision to insist on caution regarding proposals for intercommunion with Protestants.

On a return flight to Rome on Thursday from a day-long ecumenical pilgrimage to Geneva, Francis said he supported the Vatican’s Prefect for the Congregation for the Doctrine of the Faith, Cardinal-elect Luis Ladaria, in requiring a rethink of a draft proposal from the German bishops that would allow for non-Catholics to receive communion under certain conditions.

Among other items discussed during the 30-minute in-flight press conference was the global migrant and refugee situation — where, once again, Francis reiterated his support for the U.S. Catholic bishops in opposing the Trump administration’s hard line — as well as the challenges of nuclear weapons.

Last month, the Congregation for the Doctrine of the Faith (CDF) rejected the German proposal, which was approved by roughly three-quarters of the bishops during a meeting earlier in the spring. In a letter published this month, Ladaria said the proposal was “not mature enough to be published.”

Francis said that Ladaria did not act unilaterally, but with the pope’s permission, and that under the Code of Canon Law it is up to the local bishop to decide under what conditions communion can be administered to non-Catholics, not local bishops’ conferences.

“The code says that the bishop of the particular church, and that’s an important word, ‘particular,’ meaning of a diocese, is responsible for this… it’s in his hands.”

Moreover, Francis said, the problem with having an entire bishops’ conference deal with such questions is that “something worked out in an episcopal conference quickly becomes universal.”

At the same time, Francis praised the bishops’ efforts, saying their document was “well thought out with a Christian spirit.”

Whatever the German conference may come up with in the end, the pope said, likely “will be an orientational document so that every one of the diocesan bishops can determine by himself what the Code of Canon Law already permits.”

On the situation at the U.S.-Mexico border, Francis did not mince words in throwing his support behind the U.S. bishops.

“I side with them,” he said matter-of-factly, repeating what he had said in an exclusive interview with Reuters that was published on Wednesday.

“I’m proud of what the bishops of that country said,” Francis added.

More broadly, Francis said that “every country should [welcome new arrivals] with the virtue of government, which is that of prudence, because they should welcome as many refugees as they can, educate, integrate, relieve hunger, and help them find work.”

“I would say this is the tranquil, serene plan for refugees,” the pope said. “Here we’re living a wave of refugees fleeing war and hunger.”

When asked about the possibility of the Church backing away from its support of Just War Theory, Francis skirted around the question but said that we know if there is a Third World War it will be fought with nuclear weapons.

If there is a fourth, he speculated, “it will be fought with sticks,” he said—predicting the utter devastation that would follow.

Nevertheless, the pope insisted that many global challenges can be resolved.

“The problem of war, of persecution of Christians in the Middle East and also in Nigeria, the problem of hunger can be resolved,” he said. “Many countries are thinking about how to invest in those countries, invest intelligently…to give work and education.”

Recalling his lunch earlier in the day with ecumenical leaders from around the world, Francis shared the story of one individual who proposed that the first human right should be the right to hope.

“I like this,” the pope said.

At the conclusion of the press conference, Francis recognized Cardinal-elect Angelo Becciu, who has served as his sostituto, or “substitute,” in effect a sort of chief of staff.

Next week, Francis will name Becciu, along with 13 other individuals to the College of Cardinals.

Francis’s return to Rome marks the end of his much-anticipated day-long trip to Geneva to mark the 70th anniversary of the World Council of Churches, a global body promoted to working together toward ecumenical advancement.