On Sundays we could (= were allowed) to stay up late. I had a visa so I was allowed to cross the frontier. We couldn’t bring our dog into the restaurant (SU OPUESTO: «We were allowed to bring etc.). Since his accident he hasn’t been allowed to drive; As a child he had been allowed to do exactly what he liked.
[could puede tambén expresar cualquier tipo de permiso «en general,» obtenido en el pasado; refiriendonos a una acción particular permitida y llevada a cabo usamos was/were allowed en lugar de could. couldn’t puede usarse un poco más ampliamente que could. Para los tiempos de perfecto y continuos, y los tiempos pasivos, hay que usar allowed.]