The "first come, first serve" principle applies when allocating .se and .nu domain names – the first party to apply for an available domain name will be given it with no prior testing. If you believe that someone else has registered a .se or a .nu domain to which you are entitled, you can appeal the allocation of the domain name retroactively.
Learn more about dispute resolution and what to do if you believe that you are entitled to a domain name that someone else has registered. Please note that the processes are different depending on whether the matter concerns a .se or a .nu domain. You will find more information in the links here.