Global scope in Eloquent is a neat feature. However, it doesn't fit the general idea in Laravel of things being easy to implement, in that it might be very hard to remove the scope from a query, unless you know ins and outs of the Query\Builder.
That being said, you'll find here short but powerful abstract GlobalScope that your scopes will extend, and you only need to implement single method:
apply - apply any constraints on the Eloquent\Builder that your scope requires.
OPTIONALLY implement helper methods defining Eloquent\Builder macros etc.
Package requires PHP 5.4+ and works with Laravel 5/5.1.