High Court of Love by Jane Charles

With the arrival of a letter from his father’s man of business, the path of Mr. Julian Ashford’s life was altered. It also frees him to pursue the one woman he’d desired for months.
Miss Caitlin Doyle, teacher and spinster, never expected to fall in love. That is, until the spy visiting next door captured her heart. However, when she learns that he is betrothed to another, she sets aside foolish ideas of happily ever after and returns to her students.
When the two unexpectedly meet at what is supposed to be a house party, they are shocked to discover that Julian was there to be put on trial (and he isn’t the only one). The High Court of Love, something that had once existed in 15th Century France, had been revived by his aunt and the three meddlesome Tilson sisters to reform a group of rakes and rogues—the notorious Devils of Dalston. However, Julian is given one more chance to right a wrong before he is judged.
Will he be able to win Cait’s heart once again, or have his foolish decisions lost her forever?