Q1. If a marriage license is legally issued in a louisiana parish and the ceremony is conducted within 30 days by a pastor before two winesses, but that license is not filed in the clerks office after the ceremony, is that still a legal marriage.
There are three requirements for a valid contract of marriage in Louisiana: 1) the absence of legal impediment, 2) a marriage ceremony and 3) the free consent of the parties to take each other as husband and wife, expressed at the ceremony. La. C.C. art. 87. The failure to file a marriage license, even its absence altogether, does not necessarily invalidate a marriage, however, under such circumstances there often must be a factual determination made by the court as to what happened and why. In other words, the court may consider a number of factors, including whether the parties made any attempt to follow the formalities or solemnities prescribed by law, the circumstances that caused the license not to be filed, and what the couple intended at the time and how they carried on thereafter - a thorough review of the entire record and available witness testimony.
Q2. And, if the wife of this union abandons her husband 15 years later and then marries another man a year later without going through divorce e proceedings, is that marriage legal,or is this a bigamistic situation?
The answer to this question depends on whether the court determines that the parties were legally married (see above). In Louisiana, "bigamy" is the marriage to another person by a person already married and having a husband or wife living. That said, even if the first marriage is found to be invalid or null, Louisiana law may still afford the parties the right to enjoy the civil effects of marriage if it was contracted in good faith (e.g. as between themselves, the court may treat them as if they were married).