Simple as that. If there's an issue, forbid free movement between areas, or forbid the people you don't want free-moving.
Well... The agreements initially stipulated that only the citizens and their family members have free movement(of people), then it was extended to people having "long-term residency"(equivalent to a green card).
Migrants getting rapefugee status in Germany, are supposed to stay in Germany until they get citizenship or at least long term residency.
Until the Schengen area was introduced, border controls were still happening for goods and people, but much more relaxed if you had that EU passport/ID card/long-term residency permit.
Now... It's a free for all once you're in a Schengen country.
Well... The agreements initially stipulated that only the citizens and their family members have free movement(of people), then it was extended to people having "long-term residency"(equivalent to a green card).
Migrants getting rapefugee status in Germany, are supposed to stay in Germany until they get citizenship or at least long term residency.
Until the Schengen area was introduced, border controls were still happening for goods and people, but much more relaxed if you had that EU passport/ID card/long-term residency permit.
Now... It's a free for all once you're in a Schengen country.