In the Scope setup section when Accept Leads on other Owner’s behalf is selected (figure 1), any user that has the ability to edit the Lead is able to accepts it. If the option is clear, only the Owner can accept the Lead.
Owner and Admin can change the Lead Owner. The other users will see the message “This Lead is not claimed yet. You cannot change the Lead’s Owner. Only the ASPEC Administrator and can change it.”
Figure 1