I've got a marriage certificate for 1919 where, in the column for Regular/Irregular marriage there is a note of a Sheriff's Warrant and the date it is issued. I've never come across this before and I wondered if anyone could explain what it might mean.
This is just one type of irregular marriage. An irregular marriage is a marriage contracted without going through the conventional procedure of having the banns called and then being married by a minister. Irregular marriages were frowned on by the Kirk but were just as legal in the eyes of the law.
Until (I think) 1939 you could marry by declaring before witnesses that you were married. You did not need anyone to conduct the ceremony, but (from the start of statutory civil registration in 1855) in order to have the marriage registered you had to go and get a warrant from the Sheriff. You did this by getting your witnesses to come and say that they had witnessed your declaration. Then you took the warrant to the Registrar who registered the marriage.
Does this mean he really was the father?
Not necessarily. However remember that this was just after the First World War, and no doubt there were hundreds if not thousands of soldiers and sailors coming home to find they had become fathers, and wishing to regularise the situation.
Bear in mind that an illegitimate child could only be registered under its father's name if the father accompanied the mother when she went to the Registrar's to register the birth, and signed the birth certificate alongside her. A soldier's girl might give birth while he was away serving with the army, and she would not be able to put his name on the birth certificate, so the absence of a father's name on a birth certificate does not imply that there is necessarily any mystery about the father's identity.
Was he forced to marry the woman?
No.
And if he wasn't the father why would he legitimise the birth.
I would have thought he probably wouldn't, but who knows?