Form handler submit don't work
Go back and scrutinize your validation function. The code you are showing here actually works, so the problem is something you did not include in your sample.

For the reference, the working implementation over here is:

function form_newteam ($form, &amp;$form_state) {
    $form['submit'] = array(
        '#type' =&gt; 'submit',
        '#value' =&gt; 'Créer',
    );

    return $form;
}

function form_newteam_validate($form, &amp;$form_state) {
    drupal_set_message("valid");
}

function form_newteam_submit($form, &amp;$form_state) {
    drupal_set_message("submit");
}


Please note that your function names do not conform to the drupal coding standards. Function names must be prefixed with the module name. Therefore you should name your functions like this: tournament_newteam or tournament_newteam_form. If those are administrative forms, stick them into tournament.admin.inc otherwise place them into tournament.pages.inc.