While well-meaning, this law could spectacularly backfire in its current form. The widow in question did not produce any kids, she would be in charge of the Lordship with no care for its future. The widow could even legally syphon wealth, manpower and funds towards her birth House, and leave the lordship destitute after she passed away. She could pretty much do anything she wanted without any care for the consequences such as starting feuds and making long-term enemies. Why would she care what happens after she was gone when the next lord would not be of her blood?