The declaration he was forced to sign is illegal, because under the Oslo agreements Israel is only entitled to block entry to foreigners at its own borders. Which means that it can not (a) allow Feiler into Israel but then (b) deny him entry to the West Bank. Doing that means blocking him on the Green Line, and (let's all sing the song together!) the Green Line Is Not A Border. So if Israel does not want Feiler to enter the West Bank then it must deny him entry into Tel Aviv airport (or it must block his entry in the West Bank at the Allenby Bridge). But it can not allow him into Israel AND THEN block his entry into the West Bank, precisely because Israel's signature is on an agreement where it has that said it would not to do that.
from the article: Israel deports three Swedish activists with Palestinian roots