They can authorize more at the next shareholder meeting. Not sure when that is. Typically they'll double the authorization annually, if they're being a typical mREIT and expecting a typical year of SPOs. Here's a hint: let them. The last time an authorization increase got blocked (over at AGNC in early 2011) it created a mess. There's no good reason to stop the only growth vehicle an mREIT has, unless you're sure that management is buying crummy securities with the money.