osb/app/Models/Scopes/SiteScope.php

<?php

namespace App\Models\Scopes;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Scope;

class SiteScope implements Scope
{
	/**
	 * Apply the scope to a given Eloquent query builder.
	 *
	 * @param  \Illuminate\Database\Eloquent\Builder  $builder
	 * @param  \Illuminate\Database\Eloquent\Model  $model
	 * @return void
	 */
	public function apply(Builder $builder, Model $model)
	{
		// @todo Need to only do this, if the original query doesnt already have a where condition with a site_id
		$builder->where($model->getTable().'.site_id',config('site')->site_id);
	}
}