Hi all I haven't been able to find a proper answer to this yet

Basically an opponent of mine who does Blood Angels has decided he's going to take some Grey Knight allies, (Grand Master - 5 Paladins and 2 squads of 5 Terminators) now he thinks that he'll be able to deep strike them all in without scattering because of the Scouts locator beacon.

With Grey Knights only being an Allies of Convenience with Blood Angels I thought that this wouldn't be allowed but he's determined to stick with saying that they can use it because it doesn't say anywhere in the book that they can't so I'm just wondering is this true or have I missed something?