All ICANN-accredited registrars follow a uniform dispute resolution policy.  Under that policy, disputes over entitlement to a domain-name registration are ordinarily resolved by court litigation between the parties claiming rights to the registration.  Once the court rules on who is entitled to the registration, the registrar will implement that ruling.  In disputes arising from registrations allegedly made abusively (such as "cyber-squatting" and "cyber-piracy"), the uniform policy provides an expedited administrative procedure to allow the dispute to be resolved without the cost and delays often encountered in court litigation.  In these cases, you can invoke the administrative procedure by filing a complaint with one of the dispute-resolution service providers.