There are border crossings that are legal because they follow a protocol:

• holidays
• work visa
• Naturalisation procedure
• Seeking asylum
  = legal

Border crossing that does not follow a protocol:

• Clandestine border crossing
• Fictitious reasons for crossing the border
• No identity papers
  = illegal

Asylum seekers who commit criminal offences in the country that receives them are breaking the law of the receiving country and must leave the country.

The only sensible approach is that immigration, if it is not to cause stress, should be slow and moderate (i.e. follow protocols). If it doesn't, if you let a lot of foreigners - millions of them - into the country in a very short space of time, you end up in a crisis. People inevitably take an agitated stance and it usually divides the society of the host country.

So, the critical points here are

• time
• number

If a government is incapable of handling that, it is an incompetent one and should be replaced.