Ok, I'm making progress in some way.

$libraryList = Input::get('libraryList');
	$fieldToExaminate = 'job_post_library_type.library_type_id';
	$jobposts = JobPost::distinct()->where('status' ,1)->with(['libraryTypes' => function($query) use ($fieldToExaminate, $libraryList)
	{
		$query->whereIn('job_post_library_type.library_type_id', $libraryList);
	}])->get();

But I found the resulting query wrong.

SQL: select `library_types`.*, `job_post_library_type`.`job_post_id` as `pivot_job_post_id`, `job_post_library_type`.`library_type_id` as `pivot_library_type_id`
from `library_types` inner join `job_post_library_type` on `library_types`.`id` = `job_post_library_type`.`library_type_id`
where `job_post_library_type`.`job_post_id` in (4, 6, 8, 10, 12) and `job_post_library_type`.`library_type_id` in (3))

I mean, I passing only the $libraryList var that are (3) in this case. But the query is doing this job_post_library_type.job_post_id` in (4, 6, 8, 10, 12) that I don't request.

Could you help me to solve this problem?