The condition is one of three main clauses set down by the review board of the Central Mental Hospital in Dublin.
The board issued the clauses as part of a conditional discharge which saw Gallagher walk free from the hospital yesterday afternoon.
Gallagher’s family along with the Gillespie family from Ballybofey were given just a couple of hours notice before Gallagher was granted his freedom.
The families were told by Donegal Gardai that Gallagher would be released at 5pm.
However Donegaldaily.com understands he was released just after 4pm.
As part of the conditions Gallagher is allowed to visit his mother’s home at Post Office Lane in Lifford and also his late father’s grave.
However he has been warned not to contact any of the relatives of his victims Anne and Annie Gillespie who he killed in the grounds of Sligo Hospital in 1988.
Last night a spokesman for the Gallagher family said they believe a ”deal was done” before their brother handed himself into the Central Mental Hospital in May.
“When he handed himself back into the Central Mental Hospital he knew he would be out in a short space of time.
“He had it all worked out and he would never have gone in if he thought he was going to be locked up for a long time.
“He never served a day for killing those two women – he had it cushy in hospital and now he is out.
“Now it’s us who have to serve a life sentence looking over our shoulders wherever we go,” said the family spokesman.