Some carriers "whitelist" phones that can be used on their network but that is very rare. If a device doesn't meet the requirements to work in a certain country then it could be "blacklisted" or perhaps confiscated at Customes as some models of iPad where when they didn't meet Israeli wireless specifications. Generally GSM devices work almost anywhere the GSM standard is in place and though there might be nuances for some regions someone as small as Jolla needs to only worry about where there devices are being actively sold and make sure they meet certification there. Most devices sold in EU also get FCC certification even if they are not sold in the USA.