Is it permissible to encroach upon state lands and annex them to private property, justifying this by the intention to purchase them in the future, and is it permissible for anyone to encroach upon state property?

If the land in question is mawat (dead land) that has not been previously owned by anyone, then it belongs to whoever revives it. This is based on what Al-Bukhari narrated from Aisha, may Allah be pleased with her, that the Prophet, peace and blessings be upon him, said: "Whoever cultivates land that does not belong to anyone else has a greater right to it." And Abu Dawud narrated from Said ibn Zayd, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: "Whoever revives dead land, it is his." Mawat refers to desolate, uncultivated land. It is revived by irrigation, planting, cultivating, or building upon it, whereupon it becomes the property of the reviver, whether it is close to or far from inhabited areas, and whether with or without the permission of the ruler. This is the view of the majority of scholars. As for pre-emption (shufa'a), there is no basis for it here because the land is not owned by anyone. Pre-emption applies to a partner, and a neighbor has no right of pre-emption according to the majority of scholars.