Can my husband sue my sister for taking pictures of our child for a calendar?

It only takes one parent to consent to things for their child.  Only certain types of contracts are required to be evidenced by something in writing and I do not believe this falls into this category.  It sounds to me like you had a valid oral contract with your sister.  I do not believe your husband has any legal recourse against her. This answer is given in accordance with the laws of Virginia and may not be applicable in any other state.  It should not be construed as legal advice, as that would require a more thorough analysis of all of the facts involved in a specific case.  If you need further information or assistance, please feel free to contact my office for a consultation. Case results depend upon a variety of factors unique to each case. Case results do not guarantee or predict a similar result in any future case.