Sorry yes I mean "lay off" (edited). With cause obviously you can fire anyone.
In the US, an employer may 'lay off' as much staff as they want and then hire new people into those positions.
In France, for example, a 'lay off' must close the position and not hire a new body into that role for 12-24 months.
This may be difficult to prove, but the laws exist.
I like the 12-24 month waiting period as it would help reduce lay off abuse.