Tell me gang, what happens if exs decide to buy-back all the...

Tell me gang, what happens if exs decide to buy-back all the three million shares on the sell side and just kept buying them? Would that put a spanner in the works of who/whatever is manipulating this stock?
Next, is that leagal for exs to do that and is it illeagal for other sources to manipulate the price by keeping downward pressure on it?
(Disclaimer... I'm an oldie but a newbie, so please don't go screaming my head off with any obvious (to some of you) answer's.)
Thanks in advance, MTW.

here goes....big breath, hold it....now left mouse click!