Belfast man Mr Seán Ó Muireagáin was travelling home last night after Israeli authorities released him from custody.
Mr Ó Muireagáin was questioned about alleged republican activities, but his family and friends maintained he was a victim of mistaken identity.
He was released after a senior official in the Israeli government said the Shin Bet security service was satisfied that he did not pose a danger to Israeli citizens.
"It's not a concern we have," said the official. "We have real terrorists that we have to deal with and we are satisfied that that is not what we were dealing with in this case."
Mr Ó Muireagáin was arrested on Saturday, July 12th, and is known to have been questioned about alleged links between dissident republicans and Palestinian militants. He had been sending articles from Israel for the Irish language newspaper Lá when taken into custody last Saturday near Ramallah.
He was described by friends as an Irish language activist and a member of a Palestinian solidarity group. He had travelled to Israel to set up a joint Irish-Palestinian educational project to twin schools in the West Bank with schools in the North.
Mr Ó Muireagáin travelled to London from Tel Aviv and was expected in Dublin late last night.
A spokesman at the Israeli embassy in Dublin said he had not been expelled or deported from Israel. A statement said: "Morgan was under surveillance by the security service whilst in the territories and Israel."
The statement said it was confirmed that Mr Ó Muireagáin "did not yet get in contact with terror organisations" in Israel or become involved in any activities there. It said he had undertaken "amongst other things" a polygraph test, which showed that he had been telling the truth to the Israeli authorities.
The Jerusalem official said no apology would be offered to him over his detention. "It's unfortunate, but we have to exercise caution in these matters."
Earlier this week, leading SDLP politician, Mr Sean Farren, called for the Belfast man's release. "Seán Ó Muireagáin is a well known Irish language activist who has devoted a considerable amount of time to promoting Irish language activities across the North.
"His activities on behalf of the language movement were very well known and respected."