within the scope of authority
Used in formal or legal contexts to indicate that an action is taken within one's authorized powers. Often appears in business, government, or organizational settings.
This decision was made within the scope of my authority.
The department head approved the budget within his authority.
範囲内 means 'within the range/scope' more generally, while 権限内に specifically refers to the scope of one's authority.
Compound of 権限 (authority) + 内 (within) + に (adverbial particle). The exact historical derivation is straightforward; the phrase is a modern formal expression.