Can we make other family members abide by an agreement when visiting my father-in-law?

Can I create a binding contract, agreement, or rules for my sister in law and her family to follow when they make their completely disruptive visits unannounced from out of state?We sold our home (husband and three boys under age ten) and moved in with my father in law after my mom in law's death, to care for him. He wanted us, not his other adult children with him. We lived five minutes away, they live in Arizona.Sister in law, and her adult children, come from out of state unannounced and disrupt his schedule/routine and create arguments and problems, and just generally make it difficult to care for him every time they visit. He has dementia now, which is difficult to deal with as it is, and we have changed our whole lives around, accepting that my FIL and our lives have changed dramatically. SIL and family have not changed at all with Dad's situation, (he is fine as long as she is getting her way and what she wants, if she doesn't or thinks we are getting some sort of special anything, then "he must not be of sound mind.")She treats me as if I dont exist in her "parents' house", but feels I should take care of her 28 and 19 year old sons, i.e., support them and give them free room and board. Of course that isn't going to happen.She has never asked me how he was doing, or acknowledge the care I give him. Dad wanted and has legally given, my husband, power of attorney, living trust, conservator, advance medical directive - basically all responsibility for him before the dementia set in. When SIL found out his wishes, she wanted and had him tested for Alzheimer's, mental illness etc., anything in her mind to prove he wasn't of sound mind when making his decision! He checked out perfectly fine and healthy, of sound mind! She is mad angry, and threatened by all of this because she's the oldest and should "get" everything. We dont wan't anything but to create a stable environment for our family; she is fighting for "stuff" my husband said her would give her anyway.Getting to my question: can we create some sort of contract/expectations/rules for her and her family that would require prior notice of their visits, how long they will be here, who will be here, etc.? That when they are here, they are not allowed to keep him sequestered in his room, but visit in a open area. They have admitted, because of being caught red handed numerous times, to "taking" things and snooping around his property, mail, paperwork, etc. She feels the right to invade our lives because it's "her dad and his home." My husband is a 50% owner of our home. We have explained and asked, expressed our feelings about all of this, and she ignores it all.Everything she has done to take advantage of her dad she is now accusing me and my husband of doing. She tricked him into signing a power of attorney, creating a will leaving all of his poperty/money to her and her oldest son. FIL found out and that's why he wanted my husband to have the legal responsiblity for his matters. She has stolen from Dad every time she visits, and she opened an online account for his bank account without him or my husband knowing, (he's on the account as well). I could go on and on with the horrible things she has done to her Dad. One time when her aunt reminded her of all the money she "borrowed" from her dad, (over $100,000) she said, "You can't prove it." I am getting so mad just thinking of it, i need to stop typing.SO CAN WE CREATE RULES FOR HER and her family TO FOLLOW when it comes to Dad and their visits, snooping, taking money from him? She basically carries on as if she has POA, etc. If we can create a contract, so to speak, how do we make it a binding one? The POA, etc., hasn't mattered to her either, so far. (It must not be valid since it's not her name on the living trust! ; ) )Please, some advice pleassssse!