The Royal Scots ~~ some thoughts

Everybody knows The Royal Scots, the first regiment of the line, known in earlier times as the Royal Regiment of Foot and nicknamed Pontius Pilatus' bodyguard. Most sources state, correctly, that the regiment was raised in 1633 for French service as Hepburn's Regiment of Foot. The same sources mention, again correctly, that the regiment was raised by a warrant from the Privy Council of Scotland, by authority of the king. Because of this latter aspect, they claim that the regiment was raised for the Scots Establishment (and/or that it was a regiment of the British Army, a royal regiment, etc.). And that because it was a British regiment, it could be recalled by Charles II in 1661 after the Restoration.

These latter qualifications of the regiment are perhaps not fully correct.

First of all, in 1633 there was no such thing as a Scots Establishment. The whole idea of a British Army was still something for the future as well.
Secondly, all regiments for foreign service were raised under a warrant issued by the Privy Council. This way the government had, at least on paper, a little bit of control on recruitment for foreign states (on the numbers and for whom they were recruiting).
Furthermore, at the time of the Restoration the regiment was part of the French Army and its colonel owed his loyalty to the French king. It was the regimental colonel who had a contract with France, not the king of Scotland.

Looking at these considerations the following can be concluded:

Upon the raising of Hepburn's regiment in 1633, its status and position differed not much from that of other (Scots) regiments in foreign service as all were raised by a warrant that allowed recruiting. It was certainly not part of the Scots Establishment or British Army as these did not exist at that time.
The fact that the regiment survived to see the Restoration in 1660-61, that it was placed on the English Establishment and that it would eventually become the first regiment of foot, had more to do with coincidence and luck, than with anything else. That the Restoration proved be a test for the colonel's loyalty (at that time the (future) Earl of Dumbarton, who had to manage the egos of both Charles or Louis, next to looking after his own interests) (and flexibility of his loyalty), it does not imply that the regiment was a British one hired out to France. Next to this, the (positive) attitude of Charles II towards Roman Catholics (Dumbarton was Roman Catholic) at the Restoration was no doubt helpful as well. But this is different from assuming that the regiment was British and henceforth could be recalled by Charles II at will.