Unless there is a third party add-in for this, I believe this would need to be a customization to Sage 500.  I would envision something similar to Maintain Security Groups where you could assign permissions to specific GL Accounts and save by "GL Group", then a mod to Maintain Users to select the GL Group to assign to them.  With this in place, you could then modify the report processes to only report on the GL Accounts the User has permissions to. 

This is a bit of work as there are a few reports that display GL Accounts and is something you should discuss with your reseller to determine if the cost of implementing something like this makes sense or if simply allowing only certain people permissions to print the reports as they are today would be a cheaper alternative.