哈珀夫人說，她是在 "悲痛和難以理解的損失中 "尋求修改法律的，並得到了內政部長普里蒂-帕特爾和司法部長多米尼克-拉布等人的支持。
這位28歲的新婚夫婦在試圖逮捕其中一名被告時，"不知不覺 "地用雙腳踩到了牽引繩的環狀物上，從而被 "套牢 "在一輛Seat Toledo的後面。
The widow of police officer Andrew Harper said she believes he is "smiling down with pride" as the law named after him comes into force.
Mrs Harper said her quest to change the law came "in the midst of grief and incomprehensible loss", and was backed by the likes of Home Secretary Priti Patel and Justice Secretary Dominic Raab.
The 31-year-old said she was "outraged" by the prison sentences handed to the three teenagers responsible for killing her husband and felt compelled to lobby the government.
Henry Long, 19, admitted manslaughter and was sentenced to 16 years. Jessie Cole and Albert Bowers, both 18, were convicted of manslaughter after a trial at the Old Bailey and sentenced to 13 years in custody.
PC Harper was dragged for more than a mile along country lanes in Berkshire after he and a colleague responded to reports of a quad bike theft.
The 28-year-old newlywed became "lassoed" to the back of a Seat Toledo after he "unwittingly" stepped with both feet into the loop of a tow rope as he tried to apprehend one of the defendants.
PC Harper's shift had been due to end four hours before the call and he was about to begin his honeymoon.
Mrs Harper said: "I will never be rid of the hollowness that the burden of grief inflicts, but I know without hesitation that my husband Andrew would be immensely proud of this achievement in his name.
"That is why I know, without a shadow of a doubt, that he is smiling down at me with pride and love as Harper's Law, his legacy, is now achieved."
Mrs Harper said: "No longer will a family have to endure the pain of injustice in court as I did those many months ago - and that is a significantly powerful outcome.
"Throughout this journey I have met so many incredible people, fellow widows and widowers who know this unique pain I feel. I hope that this will help not only me, but all of those who have experienced these cruel atrocities."