How did British protectorate status limit Tonga's foreign affairs?

When Tonga became a British protectorate in 1900, the arrangement significantly constrained the nation's sovereignty regarding its external relations. Under the terms of the treaty with Great Britain—which was later amended in 1905—Tonga was required to conduct all of its foreign affairs through a British consul.12

This British official held veto power over both Tonga’s foreign policy and its finances, effectively limiting the kingdom's ability to act independently on the international stage. Tonga remained under this status until 1970, when it regained full control over its domestic and foreign affairs and became a fully independent nation within the Commonwealth.12