A coupls of things. Firstly the reason te IDF went back into Northern gaza is because the pals keep launching quassams from there. Secondly: The reason the Isrealis have locked down gaza is because the pals refuse to keep the quassams and terrorists in. Thirdly: Initally when the Isrealis left gaza all the border crossing were open and several were under pal control. However due to persistant terror attacks they were closed to restrict the ability of terrorists to continue their attacks. Gaza is shut down solely because it is used as a launch pad for terror attacks on Isreali's. For some reason the pals refuse to see this.
Western-backed Syrian rebels say kill foreign Islamic State (Reuters)
from the article: Hamas denies Meshal said group would consider recognizing Israel