It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Pre-emption (shuf'ah) applies where boundaries have not been fixed; once the boundaries have been fixed, there is no pre-emption."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13328