这在那时是法定的招呼形式.This mode of address was now prescribed by decree.旧制的英镑纸币已不是法定的货币了.The old pound note is no longer legal tender.你开车时不能超过法定的速度.When you drive, you must not exceed the legal limit....

“法定的”的英语可以翻译为：legal，statutory，[化] official，officinal ...