Methods decorated with the SuppressUnmanagedCodeSecurity attribute have an implicit LinkDemand placed upon all of their callers. ...

Methods decorated with the SuppressUnmanagedCodeSecurity attribute have an implicit LinkDemand placed upon all of their callers.  This LinkDemand requires that the calling code be security critical.  Marking the method which uses SuppressUnmanagedCodeSecurity as security critical makes this requirement more obvious for callers of the method.