The ONLY person that can hunt on privately owned property in Miss is the PROPERTY OWNER. Even if a person is married to the property owner, if their name is not on the deed to the land, they must have a license.
Also, the person MUST be a resident of the state of Miss to qualify. So, if your brother in law from La is hunting without a license, he is breaking the law. Even if a person owns land in Miss, they MUST be a legal resident of the state, period. You may disagree with this, but that is the way it is.
So, to answer your question, both you AND your brother in law need out of state licenses.
If you want to look it up, check out the Miss Wildlife Dept web page at;
http://mdwfp.com
And the answers to some of your questions can be found at;
http://mdwfp.com/customerService/faq.asp?Division=License
Sorry for the bad news, just wanted you to have the facts (and not let your brother in law get you in trouble.).
R
Hank