BELFAST, Jan 6 (Reuters) - A complaint of discrimination previously dismissed by Britain"s highest court against a bakery that refused to make a cake with a pro-gay message was inadmissible, the European Court of Human Rights (ECHR) ruled on Thursday. Ashers Baking in Belfast was found guilty of discrimination in 2015 for refusing to make a cake for a customer iced with the words "Support Gay Marriage" because of the owners" Christian beliefs. The bakery failed in an appeal to the local courts in 2016 but the Supreme Court, the UK"s highest judicial body, overturned that decision two years later, saying the bakers" objection was to the message on the cake, not to any personal characteristics of the messenger, or anyone with whom he was associated. Gareth Lee, a gay rights activist who had ordered the cake, argued that the Supreme Court failed to give appropriate weight to him under the European Convention of Human Rights. But the ECHR said it could not usurp the role of the local courts after Lee failed to exhaust all domestic remedies. It said this was particularly so in British-run Northern Ireland, "where there is a large and strong faith community and where the lesbian, gay, bisexual, transgender and intersex (LGBTIQ) community has endured a history of considerable discrimination and intimidation." While same-sex marriage was enacted in the rest of the United Kingdom in 2014, it was made legal in Northern Ireland only in 2020 amid opposition from the largest party in the region, the socially conservative Democratic Unionist Party. LGBTIQ support organisation, the Rainbow Project, said the decision brought the case to a close, but that there remained a number of questions around what protections exist following the 2018 Supreme Court decision. The Christian Institute, which supported the bakery owners through the courts, said the outcome was "good news for free speech and good news for Christians."