Add ace perms to it so you can control who is able to use the cmd.
i’ve read many times that script and that solved but someone still spawn vehicle, when they try to use command chat for spawn vehicle, in my screen said ( System : spawn is not valid command ) but the vehicle still spawn
Its not a script its a client native found here (FiveM Natives)
If you set it up correctly it wont let anyone spawn them in unless you want them to.
You also need to make sure there is no other ways to spawn the cars.
This works great ^_^/)
Thank you.
PS: can spawn addons cars with this?!!
PS2: yes it works 
after this line,
SetVehicleOnGroundProperly(spawned_car)
add this
Citizen.Wait(200)
SetPedIntoVehicle(PlayerPedId(), spawned_car, -1)