Good question - you could possibly do something with scopes, although you may have to do this for all models...

http://laravel.com/docs/5.1/eloquent#query-scopes

Do you not want select * to happen on every query or do you want a where clause to happen on every query? Those two are very different things.

Assuming you want to add an additional where clause to all queries, you can do something like this:

Model.php (whatever model you have)

public static function boot()
{
    static::addGlobalScope(new ClientScope);
}

Then, create the ClientScope class.

<?php

namespace App;

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

use Request;

class ClientScope implements ScopeInterface {

    public function apply(Builder $builder, Model $model)
    {
        // This is the part where you add the where clause.
        // I have no idea how you are passing the client_id though.
        // This example just assumes that you are passing an "id"
        // as a route parameter, but you may need to adjust accordingly.
        $builder->where('client_id', '=', Request::route('id'));
    }

    public function remove(Builder $builder, Model $model) {
        // Not necessary
    }
}

By SELECT * I meant do you want a where clause to happen on every query.

How about this

DB::select("SELECT * FROM users");

Will it result in SELECT * FROM users WHERE client_id = 1?

I mean what if not model was used but direct SQL query? I have to assume that some individual will try to get all information on purpose. SO I have to have a way to protect. possible?

I have the exact same problem right now. We currently decided to use only Models to access DB from our application. Did you find another solution?