Subsection (1) provides that rights and liabilities may arise between the Crown in right of Her Majesty’s Government in the UK and the Crown in right of the Scottish Administration by virtue of a contract, by operation of law, or by virtue of enactment as they may arise between subjects.
Subsection (2) provides that property and liabilities may be transferred between the Crown in such different capacities as between subjects and that they may create, vary or extinguish any property or liability as subjects may.
Subsection (3) provides that judicial proceedings in respect of property or liabilities of the Crown or the exercise of functions of office-holders of the Crown may be instituted by the Crown in either capacity and the Crown in the other capacity may be a party to the proceedings.  In appropriate cases, the Advocate General, as representing the Secretary of State, could for example institute proceedings in contract or delict against the Lord Advocate, as representing Scottish Ministers or seek judicial review of some decision taken by Scottish Ministers, such as to appoint staff in breach of the provisions referred to in section 51(3).
Subsection (4) provides that section 99 applies to a unilateral obligation as it applies to a contract.  This is because, under Scots law, legal obligations can arise, in certain cases, as a result of a promise or undertaking.
Subsection (5) defines an “office-holder” in relation to the Crown in right of Her Majesty’s Government in the United Kingdom as any Minister of the Crown or other office-holder under the Crown in that capacity and, in relation to the Crown in right of the Scottish Administration, as any office-holder in the Scottish Administration.  It defines “subject” as a person not acting on behalf of the Crown.
Commentary Part V: Miscellaneous and General Details of Provisions