This week on Utalk, a question from Laura in Lyon, France: “To prevent the influx of migrants, countries like Hungary are erecting walls. Is this legal? And is it the best way to contain illegal immigration?”

Elisabeth Vallet, Adjunct Professor of Geography and political analyst at the Université du Québec à Montréal (UQAM), answers:

“Is it legal? It’s difficult to give a clear answer because there are two angles to the question. As far as international law goes, you cannot prevent people from emigrating. But on the other hand, it is legal because most states build these walls within their own territory, where they have full sovereignty — and that’s where international law stops.

“There were about 10 walls around the world when the Berlin Wall fell. We thought they’d all come down, but that didn’t happen. Sure, borders have been scrapped in the Schengen area and as part of the North American Free Trade Agreement. But today we have 65 walls standing or being built around the worl