An employment tribunal decision could effect the way workers who are made to remain on standby after finishing their work are employed.
Nine women wardens working in sheltered homes for the elderly in the London borough of Harrow worked a basic 37-hour week, but they were kept on call for another 76 hours.
The court ruled that the council had breached working time regulations and awarded the women £1,500 compensation each.
While on standby the women could not leave the sheltered housing. The women said this led to social isolation.
As the tribunal ruled that the 76 hours on call counted as work, the women are likely to get back pay worth thousands.
Harrow Council is considering an appeal.