Does PIC 4003(b) detract from s 501?

Section 504(1) of the Migration Act 1958 (Cth) provided at the relevant time:

504 Regulations

(1)    The Governor-General may make regulations, not inconsistent with this Act, prescribing all matters which by this Act are required or permitted to be prescribed or which are necessary or convenient to be prescribed for carrying out or giving effect to this Act …

Section 501H of the Act provided at the relevant time:

501H Refusal or cancellation of visa—miscellaneous provisions

Additional powers

(1)    A power under section 501, 501A, 501B or 501BA to refuse to grant a visa to a person, or to cancel a visa that has been granted to a person, is in addition to any other power under this Act, as in force from time to time, to refuse to grant a visa to a person, or to cancel a visa that has been granted to a person.

Cross‑references to decisions under section 501

(2)    A reference in Part 5 to a decision made under section 501 includes a reference to a decision made under section 501A, 501B, 501BA, 501C or 501F.

PIC 4003(b) in Schedule 4 of the Migration Regulations 1994 (Cth) provided at the relevant time:

4003     The applicant:

…

(b) is not determined by the Foreign Minister, or a person authorised by the Foreign Minister, to be a person whose presence in Australia may be directly or indirectly associated with the proliferation of weapons of mass destruction; and …

Some of the questions to the Full Court of the Federal Court (FCAFC) were as follows:

Question 1: Are determinations made under PIC 4003(b) of Schedule 4 to the Migration Regulations 1994 (Cth) quite unlike decisions made about character under s 501 of the Migration Act 1958 (Cth)?

Question 2: It it clearly inconsistent or clearly lacking in harmony for there to coexist "a power to refuse a particular class of visa for failure to satisfy certain criteria set out in subordinate legislation and a power to refuse to grant a visa on character grounds under the Migration Act"?

Question 3: Does PIC 4003(b) detract from, or impair the operation of, and is therefore repugnant to, s 501? In other words, can it be said that "the subject matter of s 501 deals completely, and thus exclusively, with the subject matter of PIC 4003(b) with the result that the latter detracts from or impairs the operation of s 501"?

Question 4: Can it be said that, "where a statute purports to cover its subject matter exhaustively, any other legislation which purports to cover that subject matter may be repugnant, if it operates to detract from or impair the operation of the exhaustive legislation"?

The FCAFC answered those questions as follows: