Interesting information from Americans for Peace Now, Settlement Watch:

The owners of the Migron land are Palestinian residents of the villages of Deir Dibwan and Burka. The land on which the outpost was built was registered in the land registry in the name of the Palestinian owners from before 1967 (two of the land owners who originally petitioned the High Court to stop Migron have since died, with the case now passed on to their heirs). The Civil Administration's land registration division has in its possession all of the relevant ownership papers. Indeed, in response to Peace Now's petition, the state submitted an aerial photo confirming the claims of the landowner map. (Scanned versions of the relevant ownership documents and the aerial photo are available here, page 6). Peace Now recently released a video introducing the world to these owners.

Israeli officials have repeatedly confirmed, formally and on the record, that the land on which the outpost of Migron is built is legally owned by Palestinians.

"Nature of land rights: Private Palestinian land (agricultural lands of 'Ein Yabrud and Burka). Body which allocated the land: None." (March 2005 Sasson Report, comments regarding Migron - English translation)

"The land on which the buildings of the outpost were built is registered Palestinian land within the boundaries of the villages of Burka and Deir Dibwan." (Civil Administration declaration, December 2006, made by Brig. Gen. Kamil Abu Rukon, Head of the Civil Administration in the West Bank)

"The land upon which the buildings of the outpost were constructed is registered
privately owned Palestinian land, part of the agricultural terrain within the boundaries of Burka and Dir Debwan...." ( December 2006, statement of the State of Israel to the High Court of Justice in response to Peace Now petition against Migron)