Normally it's not possible because he has to be dead to have a widow.
It might be possible to be declared legally dead, which would result in a legal divorce and inheritance. So then technically anyone who later turned up actually alive might have to remarry his spouse, assuming she had not married someone else already. In that case, he might marry his wife's sister, but his first wife would be his ex-wife, not his widow.
Perhaps you are asking whether it is legal for a man (a widower) to marry the sister of his late wife? If that's the case it is perfectly legal for him to marry the lady. She is no blood relation of his and the fact he was married to her sister, now deceased, has no bearing on their legal union in most Western cultures and all US states including California.
So far, I believe it's still illegal for anyone to marry a dead person no matter who they are or where they live. But it's 2012 so that may change if people want it too badly enough; perhaps if the family of the deceased can prove that the deceased person would have agreed to the union if they had been alive. This is a crazy world you know. People have wed outside their own species already, so it's not that far a stretch to imagine it.
a priest
no because if its a widow then he man is dead and a dead person cant marry a living person!
Your brother or sister can never become your brother-in-law or sister-in-law. The people they marry are your brother-in-law or sister-in-law. Oh, yes, in a riddle, if your brother marries your sister, then your brother and sister are also your brother-in-law and your sister-in-law. But that kind of marriage is forbidden everywhere and by all modern religions, so it is a pretty poor riddle.
There are no laws preventing it. However, it is an impossibility since the man is dead.
only id he had power of attorney for after he was deceased
"Is it legal for a man in Scotland to marry his widow's sister?" His widows sister surely mean he's dead or his widow wouldn't be his widow!!, However if he had faked his death so he could then run off with and then marry his widows sister then this would be bigamy which is illegal in UK law.
Except that he has to be dead to have a widow, it might be legal.(see related question)
no. because he is deceased
If it's his widow...he's dead; he ain't marrying anybody!
No, it is illegal to marry your sister anywhere in the world.
It is legal to marry a second cousin in California. It is not legal to marry anyone else in your family. California also allows first cousin marriage.
This is legal for a man to marry his widow's sister in France.
no, but impossible as well, unless she plans dying soon to join you
because if a woman is a widow that means her husband has died. Therefore a man cannot marry his widows sister because HE is dead!
It is legal for a man in France to marry his widow's sister. These people are not related and there is no problem with marrying.
Your cousin's sister is also your cousin. In some places it is legal to marry your cousin.