Firstly as has been pointed out by the usual standards Margaret is the legal heir.
Henry VII's accession (by right of conquest) technically extinguished the rights of anyone else - of course might is always right, but at this period there isn't anyone powerful enough and in the right position to challenge Margaret's rights to inherit the throne.
More than likely the nobility and power breakers will be split - some for Margaret, some perhaps for Mary, others pointing to Courtenay, to the Poles and to Buckingham.
In that the council most likely confirms Margaret as heir and her and James travel south at speed.
Secondly as has been pointed out - James rights as Margaret's husband would be well understood at the period and in the context of the time everything Margaret was possessed of was his by convention and law. There is nothing in her marriage treaty to limit his rights in the event of her accession.
However, what is likely is that Margaret's first Parliament will attempt to impose some limits on James as they meet to confirm Margaret's hereditary rights to the dues of a sovereign, largely I suspect they'll ban him from appointing Scots to English positions, prevent him from ammending the succession and confirming that in the event of Margaret's death without issue his rights in England die with her. Suspect these will be hammered out in a bargain with James and Margaret - in return they'll accept him as King by name etc.
For the English they are getting a reasonably good deal - a true Renaissance prince who had proved himself to be a capable ruler.
In terms of alliances - James is already allied with both England and France, England's relationship with Spain was hardly fixed or historic - so there's no guarantee which way James and Margaret will jump.
They are only going to stick with Mary's Spanish match if a) Charles comes to the wicket (in OTL he was reluctant to jump into marriage which is why he married relatively late after a string of broken betrothals) b) they don't need a political match elsewhere in the event they decide to join in the continental wars
Quite frankly its just as likely that Charles will break the match if it no longer suits him politically - on his accession in Spain he was pushed towards Isabella (partially because the Spanish court wanted a Spanish match to contrast with his foreign upbringing) in OTL.
Mary's options have suddenly improved however, she is now heiress presumptive - that means James will want her married where it best suits him if his wife fails to produce an heir.
Mary's attractiveness to Maximilian and Ferdinand and a raft of others has also just shot up - which might mean pressure on Charles to actually pursue the betrothal and marry her - though of course the problem is Charles is 9 to Mary's 13 - and a lot can change before Charles is of legal age to actually turn betrothal into marriage.
Henry VII's accession (by right of conquest) technically extinguished the rights of anyone else - of course might is always right, but at this period there isn't anyone powerful enough and in the right position to challenge Margaret's rights to inherit the throne.
More than likely the nobility and power breakers will be split - some for Margaret, some perhaps for Mary, others pointing to Courtenay, to the Poles and to Buckingham.
In that the council most likely confirms Margaret as heir and her and James travel south at speed.
Secondly as has been pointed out - James rights as Margaret's husband would be well understood at the period and in the context of the time everything Margaret was possessed of was his by convention and law. There is nothing in her marriage treaty to limit his rights in the event of her accession.
However, what is likely is that Margaret's first Parliament will attempt to impose some limits on James as they meet to confirm Margaret's hereditary rights to the dues of a sovereign, largely I suspect they'll ban him from appointing Scots to English positions, prevent him from ammending the succession and confirming that in the event of Margaret's death without issue his rights in England die with her. Suspect these will be hammered out in a bargain with James and Margaret - in return they'll accept him as King by name etc.
For the English they are getting a reasonably good deal - a true Renaissance prince who had proved himself to be a capable ruler.
In terms of alliances - James is already allied with both England and France, England's relationship with Spain was hardly fixed or historic - so there's no guarantee which way James and Margaret will jump.
They are only going to stick with Mary's Spanish match if a) Charles comes to the wicket (in OTL he was reluctant to jump into marriage which is why he married relatively late after a string of broken betrothals) b) they don't need a political match elsewhere in the event they decide to join in the continental wars
Quite frankly its just as likely that Charles will break the match if it no longer suits him politically - on his accession in Spain he was pushed towards Isabella (partially because the Spanish court wanted a Spanish match to contrast with his foreign upbringing) in OTL.
Mary's options have suddenly improved however, she is now heiress presumptive - that means James will want her married where it best suits him if his wife fails to produce an heir.
Mary's attractiveness to Maximilian and Ferdinand and a raft of others has also just shot up - which might mean pressure on Charles to actually pursue the betrothal and marry her - though of course the problem is Charles is 9 to Mary's 13 - and a lot can change before Charles is of legal age to actually turn betrothal into marriage.