Enlighten me, how does it mean we've lost Gibraltar?
Frontex and Gibraltar border staff and free movement doesn't seem like any great threat to Gibralatars sovereignty to me unless I'm missing something?
Uncontrolled, free movement, of unemployed, drug dealing, criminal Spaniards and others from anywhere in the
Schengen zone . . . into Gibraltar . . . how else should it be described ?!

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From the link . . .
The Spanish workers of La Línea de la Concepción are at the ready to celebrate the removal of the Gibraltar border controls. And they have reason to.
This
small coastal town bordering Gibraltar is one of the poorest in Spain. A
third of people here are unemployed and in some neighbourhoods that figure rises to 80%.
Drug trafficking from Morocco and armed gangs have become a problem for police.
image caption: Gibraltar is an essential source of work for people living in La Línea.
Fifteen thousand residents have jobs in Gibraltar where wages are on average 20% higher. And Gibraltar needs them for the lifeblood of its economy, especially in the nursing, catering and cleaning industries.
What will change
As part of the UK's exit from the EU, the UK and Spain have agreed in principle that
the land border will go, possibly within six months, but the terms of the deal first have to be made into a formal treaty with the EU:
- The single road linking the territories will be widened to allow people and cars to travel freely.
- Some infrastructure will stay at the border, a few guards will remain on standby, and finalities still need to be worked out such as judging the necessity of certain customs checks away from the border and if so how they would work.
- For the border to disappear, Gibraltar will effectively become part of Europe's passport-free travel area - the Schengen zone - though there is a different use of language from both sides on whether it will be "part of", or "connected to" Schengen
- With the border gone, new arrivals will only be checked if they enter by sea at the port and by air
- For the first time, as well as the Gibraltar border guards, there will be guards from the EU border and Coastguard Agency known as Frontex also checking passports ( . . . of all those that enter Gibraltar, by sea at the port and by air).