The Israeli Security Wall doesn't breach international law, and many countries are doing far worse things in spite of international laws. Israel is simply protecting its borders and defending against outside threats. With that in mind, the security wall is a smart idea that keeps intruders out without causing too much harm to the surrounding area.
No, the Israeli security wall is not inconsistent with international law, because it is common for a nation to put up a security wall in order to defend its border. Israel has a larger problem with security than most nations have, so Israel has all the more interest in defending itself. Israel's wall is the only way to prevent terrorists from walking into the country.