forge/app/Models/Scopes/PublishedScope.php

<?php

namespace App\Models\Scopes;

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

class PublishedScope implements Scope
{
    /**
     * Apply the scope to a given Eloquent query builder.
     */
    public function apply(Builder $builder, Model $model): void
    {
        $builder->whereNotNull($model->getTable().'.published_at')
            ->where($model->getTable().'.published_at', '<=', now());
    }
}