If you don't have too many teams, you can just use the "edit score" permission for those users and use multiple limitations at the team level.
Otherwise, you can hack the admin_files/editscore.php file (you should upgrade to Version 1.2 if you haven't already). At line 203:
// Show all teams if user has full or conference access
if ($is_admin || $is_manage_score || $is_manage_score_conf) {
You can remove the last two conditions to make it so that only administrator users can change teams:
if ($is_admin) {
Make the same change at line 277.
If you really must stick with a Version 1.0 or 1.1 installation, you can look for those similar code snippets in update.php.