It seems that Old Law only became an island at some point between 1769 (Armstrong's map) and 1820 (Fryer's map).
Ross Back Sands are only accessible on foot. There is an informal parking area for a dozen or so cars at the end of the public road at Ross (grid reference). There are no road signs to the beach. When I arrived at about 8.45 on a weekday morning there were only a couple of cars there but by the time I left 2 hours later the parking area was full. It is a flat walk of just over a mile from the parking area north east along the only public footpath, which first passes some holiday cottages, then crosses a field (full of placid cows when I visited) before entering an area of rough grazing, which soon becomes sand dunes. Once you get to the beach, you then have to turn north west and walk up the beach for 2km in order to reach the crossing point to Old Law. The day I visited was a particularly low tide and I don't know how long the island is cut off for on an average tide. It was a bit of a trudge along the beach, as the sand is a bit soft in places.
A 25" to a mile scale Ordnance Survey map from 1898 shows a lifeboat house and well located in the middle of the island but towards the southern end. These were marked as disused on a 1922 map and they are not shown at all on modern OS maps.
There are two prominent tall navigation beacons at Guile Point on the northern end of Old Law, one on the foreshore and one in the dunes. They look a bit like industrial chimneys. I only explored the southern tip of the island, although I had seen the daymarks from Holy Island a couple of days previously.
Map showing the location of Old Law
Looking north towards Old Law
Looking south east over Ross Back Sands towards the Farne Islands
Ross Point from Old Law
Old lobster pot on the south coast of Old Law
Looking south from Old Law across Wide Open towards Ross Back Sands
Pirri-pirri bur
This is an invasive non-native species from New Zealand
Salt marsh separating Old Law from Ross Point
No public access beyond this point
Looking south east from Old Law towards the Farne Islands
Marram grass on Old Law
Looking north up the east coast
Looking south east over Ross Back Sands towards the Farne Islands
Improvised seat on the east coast of Old Law
Lindisfarne Castle from Old Law
Looking north up the east coast of Old Law towards Lindisfarne Castle
Navigation beacons at Guile Point from Holy Island