Is it permissible for the two parties to the marriage contract (the man and the woman's guardian) to delegate two other individuals in a third country to complete the contract, with the presence of the officiant (ma’dhoun) and witnesses? And is a telephonic authorization sufficient, or does it require an official power of attorney from a court?

It is permissible for both the guardian (wali) and the husband to appoint an agent (wakil) in the marriage contract. The contract is valid if the guardian's agent makes the offer of marriage to the husband's agent, and the husband's agent accepts it in the presence of two witnesses. The form of authorization (tawkeel) is valid with anything that indicates it, and agency is valid for both the offer (ijab) and acceptance (qabul). It is also permissible to authorize via telephone.