Is it permissible for the maternal uncle to be the guardian (wali) for his sister's daughter in marriage and to solemnize her marriage contract?

The marriage contract performed by the maternal uncle (khal) is valid in specific situations: First, if the maternal uncle is authorized by the father or the legal guardian. Second, if he acts as a guardian in the absence of agnates, which is an opinion held by some scholars. Third, if the maternal uncle's contract is conducted in the presence of the woman's guardian, with his explicit consent or implicit consent through silence. Fourth, if the contract is concluded and documented in an Islamic country that permits the maternal uncle to marry off his niece or allows a contract without a guardian, because the ruling of a judge in matters of ijtihad (independent legal reasoning) cannot be overturned.